Patent Publication Number: US-2023141994-A1

Title: Quantum internet router

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/776,265, filed Jan. 29, 2020, which application claims the benefit of U.S. Provisional Patent Application No. 62/798,620 , filed Jan. 30, 2019. Both prior filed applications are expressly incorporated by reference herein in their entirety. 
    
    
     BACKGROUND 
     The field of the disclosure relates to Internet communications, and more specifically to a quantum Internet router. 
     Traditional Internet communications include a network of nodes (e.g., network nodes, Internet routers). The network nodes may receive and forward digital data based on routing information associated with the digital data. These network nodes may be coupled with each other by classic channels such as a digital information channel. The channels may be formed by a communication line (e.g., coaxial cable, fiber-optic cable). Digital information channels may suffer from security and processing limitations. In contrast, quantum computers and quantum communications may provide enhanced processing capability and security, but have inherent limits of transmission mediums (e.g., optical signals) due to attenuation. 
     SUMMARY 
     The described techniques relate to improved methods, systems, devices, or apparatuses that support a quantum Internet router. Generally, the described techniques provide for a router within a network of nodes that is configured to route and transport a quantum state (e.g., a qubit) of a particle. That is, a qubit may be transported from a source network node to a destination network node by one or more distributed network nodes (e.g., quantum Internet routers). A network node configured to transport qubits may be coupled with one or more other network nodes by classic channels (e.g., a digital information channel) and one or more quantum entangled channels (e.g., established using entangled particle (EP) pairs). The network node (e.g., a first network node) may receive a command from a second network node via the digital information channel The command may include an indication of the destination network node, a Bell State Measurement (BSM), and an identifier of EPs corresponding to a quantum entangled channel The first network node may perform a quantum state recovery (QSR) operation using the BSM and the identified EPs to determine the qubit being transported to the destination network node. Additionally, the first network node may reference a forwarding table (e.g., stored in memory at the first network node) to determine a network node for forwarding of the command (e.g., a third network node). Based on the determined third network node, the first network node may select an EP associated with a quantum entangled channel between the first network node and the third network node. Using the selected EP and the qubit, the first network node may generate a second BSM. The first network node may transmit a command to the third network node by a digital information channel, the command including the indication of the destination network node, the second BSM, and an identifier of the EPs used to generate the second BSM. Each of the network nodes of the distributed network nodes may perform similar operations until the destination network node receives the command and recovers the quantum state of the qubit for processing. 
     A method at a first network node is described. The method may include receiving, from a second network node via a first digital information channel, a first command indicating a destination network node and a first BSM associated with a first entangled particle of a first pair of EPs that establish a first quantum entangled channel between the first network node and the second network node, and selecting, based on the destination network node, a third network node from a set of network nodes, where the first network node includes one or more EPs each associated with respective ones of one or more pairs of EPs that establish respective quantum entangled channels between the first network node and each network node of the set of network nodes. The method may further include generating a second BSM based on the first BSM and the first entangled particle and associated with a second entangled particle of a second pair of EPs of the one or more pairs of EPs that establishes a second quantum entangled channel between the first network node and the third network node, and transmitting, to the third network node by a second digital information channel, a second command indicating the destination network node and the second BSM. 
     A first network node is described. The first network node may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the first network node to receive, from a second network node via a first digital information channel, a first command indicating a destination network node and a first BSM associated with a first entangled particle of a first pair of EPs that establish a first quantum entangled channel between the first network node and the second network node, and select, based on the destination network node, a third network node from a set of network nodes, where the first network node includes one or more EPs each associated with respective ones of one or more pairs of EPs that establish respective quantum entangled channels between the first network node and each network node of the set of network nodes. The instructions may be further executable by the processor to cause the first network node to generate a second BSM based on the first BSM and the first entangled particle and associated with a second entangled particle of a second pair of EPs of the one or more pairs of EPs that establishes a second quantum entangled channel between the first network node and the third network node, and transmit, to the third network node by a second digital information channel, a second command indicating the destination network node and the second BSM. 
     Another first network node is described. The first network node may include means for receiving, from a second network node via a first digital information channel, a first command indicating a destination network node and a first BSM associated with a first entangled particle of a first pair of EPs that establish a first quantum entangled channel between the first network node and the second network node, and means for selecting, based on the destination network node, a third network node from a set of network nodes, where the first network node includes one or more EPs each associated with respective ones of one or more pairs of EPs that establish respective quantum entangled channels between the first network node and each network node of the set of network nodes. The first network node may further include means for generating a second BSM based on the first BSM and the first entangled particle and associated with a second entangled particle of a second pair of EPs of the one or more pairs of EPs that establishes a second quantum entangled channel between the first network node and the third network node, and means for transmitting, to the third network node by a second digital information channel, a second command indicating the destination network node and the second BSM. 
     A non-transitory computer-readable medium storing code at a first network node is described. The code may include instructions executable by a processor to receive, from a second network node via a first digital information channel, a first command indicating a destination network node and a first BSM associated with a first entangled particle of a first pair of EPs that establish a first quantum entangled channel between the first network node and the second network node, and select, based on the destination network node, a third network node from a set of network nodes, where the first network node includes one or more EPs each associated with respective ones of one or more pairs of EPs that establish respective quantum entangled channels between the first network node and each network node of the set of network nodes. The code may further include instructions by the processor to generate a second BSM based on the first BSM and the first entangled particle and associated with a second entangled particle of a second pair of EPs of the one or more pairs of EPs that establishes a second quantum entangled channel between the first network node and the third network node, and transmit, to the third network node by a second digital information channel, a second command indicating the destination network node and the second BSM. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for performing, based on the first BSM and the first pair of EPs, a QSR operation to determine a quantum state of a source particle associated with the first command, where generating the second BSM may be based on the quantum state of the source particle associated with the first command 
     Some cases of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving, from a control node, more than one entangled particle each associated with a respective pair of EPs that establishes a quantum entangled channel between the first network node and the second network node, where the more than one entangled particle includes the first entangled particle. 
     Some instances of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving, from the control node, a set of identifiers identifying the respective pairs of EPs, where the first command further includes a first identifier of the set of identifiers identifying the first pair of EPs. 
     Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting, to a control node, an indication of receiving the first command indicating the first BSM associated with the first pair of EPs that establish the first quantum entangled channel between the first network node and the second network node, and receiving, from the control node, a third entangled particle associated with a third pair of EPs that establishes a third entangled channel between the first network node and the second network node. 
     Some cases of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving the first command indicating the first BSM associated with the first pair of EPs that establish the first quantum entangled channel between the first network node and the second network node decreases a quantity of quantum entangled channels between the first network node and the second network node by one, and transmitting the indication may be based on the quantity of quantum entangled channels between the first network node and the second network node being less than a threshold quantity of entangled channels between the first network node and the second network node based on decreasing the quantity of quantum entangled channels between the first network node and the second network node by one. 
     In some instances of the method, apparatuses, and non-transitory computer-readable medium described herein, the selecting the third network node further includes referencing a forwarding table, where the forwarding table indicates the third network node based on the destination network node. 
     In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the first command further indicates an identifier of the first pair of EPs, and the second command further indicates an identifier of the second pair of EPs. 
     Some cases of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving, from a fourth network node of the set of network nodes different than the second network node, a third command indicating a second destination network node and a third BSM associated with a third pair of EPs of the one or more pairs of EPs that establish a third quantum entangled channel between the first network node and the fourth network node. 
     In some instances of the method, apparatuses, and non-transitory computer-readable medium described herein, the first network node may be different than the destination network node, and selecting the third network node may be based on the first network node being different than the destination network node. 
     An apparatus is described. The apparatus may include a set of quantum entangled channel interfaces each configured to receive one EP of a pair of EPs to link the apparatus and one of a set of network nodes, a set of digital information channel interfaces each configured to receive a set of commands from one of the set of network nodes, where each command of the set of commands indicates a destination network node and a first BSM associated with one quantum entangled channel interface of the set of quantum entangled channel interfaces, and memory configured to store a forwarding table indicating to which of the set of network nodes to forward commands of the set of commands based on the destination network node, where the forwarded commands include a second BSM based on the first BSM. 
     Some examples of the apparatus may include circuitry configured to perform a QSR operation to determine a quantum state of a source particle associated with each of the set of commands based on the first BSM and the one EP received by the one quantum entangled channel interface. 
     In some cases, the set of quantum entangled channel interfaces includes more than one quantum entangled channel interface associated with each of the set of network nodes. 
     In some instances, each of the set of digital information channel interfaces may be further configured to transmit the forwarded commands to one of the set of network nodes indicated by the forwarding table. 
     In some examples, each of the set of commands includes a first identifier of a first pair of EPs including an EP received by the one quantum entangled channel interface associated with the first BSM, and each of the forwarded commands includes a second identifier of a pair of a second pair of EPs to link the apparatus and a network node of the set of network nodes indicated by the forwarding table. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates an example of a system that supports a quantum Internet router in accordance with aspects of the present disclosure. 
         FIG.  2    illustrates an example of a configuration of a network node that supports a quantum Internet router in accordance with aspects of the present disclosure. 
         FIG.  3    illustrates an example of a process flow that supports a quantum Internet router in accordance with aspects of the present disclosure. 
         FIG.  4    shows a block diagram of a network node that supports a quantum Internet router in accordance with aspects of the present disclosure. 
         FIG.  5    shows a flowchart illustrating a method that supports quantum Internet router in accordance with aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In some Internet communication systems, network nodes are configured to communicate digital information (e.g., bits) by classic channels (e.g., digital information channels such as Ethernet channels, Asynchronous Transfer Mode channels) between a network of nodes. Digital information channels may be carried over electrical cables (e.g., twisted pair such as Cat 5e cable or Cat 6 cable) or fiber optic cables. In some cases, it may be desirable for these nodes to communicate quantum information (e.g., qubits). But transmission of an instance of a quantum photon may be limited due to attenuation of the optical signal. Additionally, the instance of the quantum photon may not be cloned or amplified to extend a possible transmission distance of the instance of the quantum photon. Instead, the network nodes may utilize a quantum teleportation protocol to transfer a quantum state between network nodes. Here, the quantum state of a particle (e.g., a photon) may be transferred from a first photon to a second photon by entangled particles (EPs). In principle, this may enable network nodes transmit a quantum state of a particle along a chain of EP links (e.g., quantum entangled channels). Thus, the network nodes may be enabled to receive and route quantum states based on a destination network node. 
     Generally, the described techniques provide for an Internet router within a network of nodes that is configured to transport a quantum state of a particle to one of multiple other nodes. A network node configured to transport qubits may be coupled with one or more other network nodes by classic channels (e.g., a digital information channel) and one or more quantum entangled channels (e.g., established using EP pairs). The network node (e.g., a first network node) may receive a command from a second network node by the digital information channel. The command may include an indication of the destination network node, a Bell State Measurement (BSM), and an identifier of EPs corresponding to a quantum entangled channel. The first network node may perform a quantum state recovery (QSR) operation using the BSM and the identified EPs to determine the qubit being transported to the destination network node. Additionally, the first network node may reference a forwarding table (e.g., stored in memory at the first network node) to determine a network node to forward the command to (e.g., a third network node). Based on the determined third network node, the first network node may select an EP associated with a quantum entangled channel between the first network node and the third network node. Using the selected EP and the qubit, the first network node may generate a second BSM. The first network node may transmit a command to the third network node by a digital information channel, the command including the indication of the destination network node, the second BSM, and an identifier of the EPs used to generate the second BSM. Each of the network nodes of the distributed network nodes may perform similar operations until the destination network node receives the command 
     Aspects of the disclosure are initially described in the context of a system. Aspects of the disclosure are further described in the context of a network node and a process flow. Aspects of the disclosure are further illustrated by and described with reference to block diagrams and a flowchart that relate to a quantum Internet router. 
       FIG.  1    illustrates an example of a system  100  that supports a quantum Internet router in accordance with various aspects of the present disclosure. The system  100  may be an example of an Internet communications system  100  configured to communicate digital information (e.g., bits) and quantum state information (e.g., qubits). The system  100  includes a source network node  105 , network nodes  110 , and a destination network node  150 . Each of the network nodes  105 ,  110 , and  150  may be in communication with one or more other network nodes  105 ,  110 , or  150  by a digital information channel  120  and at least one quantum entangled channel  125 . The network nodes  105 ,  110 , and  150  may also be in communication with one or more control nodes  135  configured to communicate EP transmissions  130  to the network nodes  105 ,  110 , and  150 . 
     Each of the quantum entangled channels  125  may be configured by a control node  135  (e.g., an EP creation node). A control node  135  may generate a pair of EPs  115  and transmit each of the pair of EPs  115  to different ones of two network nodes  105 ,  110 , or  150 . For example, the control node  135 - a  may generate a pair of EPs  115  and transmit a first EP  115  of the pair of EPs  115  to the source network node  105  by the EP transmission  130 - a . Additionally, the control node  135 - a  may transmit a second EP  115  of the pair of EPs  115  to the network node  110 - a  by the EP transmission  130 - b . The control node  135  may additionally transmit an identifier of the pair of EPs  115  to both of the network nodes receiving the pair of EPs. Thus, the control node  135 - a  may configure a quantum entangled channel  125  between the source network node  105  and the network node  110 - a  associated with the identifier of the pair of EPs  115 . In some cases, the control nodes  135  may configure more than one quantum entangled channel  125  between network nodes  105 ,  110 , or  150 . For example, the control node  135 - b  may configure multiple quantum entangled channels (e.g., two, three, four) between network node  110 - a  and  110 - b  (e.g., by generating EP pairs and transmitting EPs  115  to the network nodes  110 - a  and  110 - b  by EP transmissions  130 - c  and  130 - d , respectively). 
     The controller  140  may issue commands to the control nodes  135  to generate additional pairs of EPs  115 . For example, when a quantum entangled channel  125  is used by a network node  105 ,  110 , or  150 , that quantum entangled channel  125  may be extinguished because the wave functions of the associated EPs are collapsed by measurement. To ensure that the network nodes  105 ,  110 , and  150  maintain quantum entangled channel communications, the controller  140  may issue a command to one of the control nodes  135  to create a pair of EPs  115  and communicate them to two network nodes  105 ,  110 , or  150 . In some cases, the controller  140  may receive an indication when a quantum entangled channel  125  is used. Based on the indication, the controller  140  may determine whether an additional pair of EPs is to be generated by a control node  135 . For example, if a quantity of quantum entangled channels between two network nodes  105 ,  110 , or  150  falls below a threshold (e.g., two quantum entangled channels), the controller  140  may issue a command to a control node  135  to generate an additional pair of EPs  115  to establish a new quantum entangled channel  125  between the two network nodes  105 ,  110 , or  150 . For example, if the network node  110 - b  uses a quantum entangled channel  125 - d  to communicate a quantum state of a particle to the network node  110 - d , the network node  110 - b  or network node  110 - d  may indicate the use of the quantum entangled channel  125 - d  to the controller  140 . The controller  140  may issue a command to the control node  135 - c  to generate a pair of EPs  115 . The control node  135 - c  may generate the pair of EPs  115  and communicate a first EP  115  to the network node  110 - b  and a second EP  115  of the pair of EPs  115  to the network node  110 - d , establishing an additional quantum entangled channel  125 - d  between the two network nodes  110 - b  and  110 - d.    
     The source network node  105  may determine a source particle  145  for transmission to a destination network node  150 . In some cases, the source network node  105  may be unable to transmit the source particle  145  directly to the destination network node  150 . For example, a distance between the source network node  105  and the destination network node  150  may be greater than a distance that a quantum photon may be transmitted without significant amounts of attenuation. Instead, the source network node  105  may determine to transmit the quantum state of the source particle (e.g., a qubit indicating the quantum state of the source particle  145 ) to the destination network node  105  by a series of quantum entangled channels  125  and network nodes  110 . 
     To communicate the quantum state of the source particle  145  to network node  110 - a , the source network node  105  may perform a BSM operation with the source particle  145  and one of the EPs  115 - a . Thus, the source network node  105  may cause the source particle  145  and the EP  115 - a  to collapse into a classical state (e.g., the source particle and the EP  115 - a  may no longer be quantum particles). The source network node  105  may transmit, by the digital information channel  120 - a , the BSM result to network node  110 - a . For example, the source network node  105  may transmit a command by the digital information channel  120 - a  including the BSM result. The command may further include an indication of the destination network node  150  and an identifier or the EP  115 - a  used to determine the BSM result. An example command may be QTP://QIR1?src=‘Source’&amp;Dest=‘Dest’UBSM=. . . &amp;epid=1. Here, the command may include an indication of the next network node  110 - a  (e.g., the network node  110  for the next hop, QIR1) source network node  105  (e.g., Source), an indication of the destination network node  150  (e.g., Dest), the BSM result (e.g., . . . ), and an identifier of the EP  115 - a  used to generate the BSM result (e.g., 1). 
     The network node  110 - a  may receive the command and recover the quantum state of the source particle  145  based on the command For example, the network node  110 - a  may identify one of the EPs  115 - b  associated with the BSM indicated within the command based on the identifier of the EP  115 - a  within the command The network node  110 - a  may perform a QSR operation to determine the quantum state of the source particle  145  based on the identified EP  115 - b  and the BSM. Because the identified EP  115 - b  and the EP  115 - a  used to generate the BSM are from a same pair of EPs (e.g., EPs  115 - a  and  115 - b  may be measured to have opposite spins), the network node  110 - a  may determine the quantum state of the source particle  145  based on performing the QSR operation using the identified EP  115 - b  and the BSM result. 
     The network node  110 - a  may reference a forwarding table (e.g., stored at the network node  110 - a ) to determine to which network node  110  to forward the command Here, the network node  110 - a  is in communication with three network nodes (e.g., the source network node  105 , network node  110 - b , and network node  110 - c ), but in other examples, the network node  110 - a  may be coupled with more network nodes  110  or less network nodes  110 . The forwarding table may indicate either network node  110 - b  or network node  110 - c  based on the destination network node  150 . For example, the forwarding table may indicate a network node  110  to minimize a number of hops (e.g., a number of network nodes the command is forwarded between prior to being forwarded to the destination network node), to maximize a reliability of the transmission (e.g., based on a reliability of the digital information channels  120  or the quantum entangled channels  125 ), or some other predetermined factor. An example forwarding table is shown below in table 1. The ‘Node’ may indicate a current node (e.g., here, network node  110 - a ), the ‘Destination’ may correspond to an Internet protocol address of the destination network node  150 , the ‘Forwarding Interface’ may indicate a next network node  110 , and the ‘Link Metric’ may indicate a rank of the corresponding interface. For example, a lower link metric value may correspond to a more favorable forwarding interface. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Forwarding Table 
               
            
           
           
               
               
               
               
            
               
                   
                   
                   
                 Link 
               
               
                 Node 
                 Destination 
                 Forwarding Interface 
                 Metric 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 Source Network Node 
                 192.168.0.0/16 
                 Network Node 110-a 
                 1 
               
               
                 105 
               
               
                 Network Node 110-a 
                 192.168.0.0/16 
                 Network Node 110-b 
                 10 
               
               
                 Network Node 110-a 
                 192.168.0.0/16 
                 Network Node 110-c 
                 1 
               
               
                 Network Node 110-b 
                 192.168.0.0/16 
                 Network Node 110-d 
                 1 
               
               
                 Network Node 110-c 
                 192.168.0.0/16 
                 Network Node 110-d 
                 1 
               
               
                 Network Node 110-d 
                 192.168.0.0/16 
                 Destination Network 
                 1 
               
               
                   
                   
                 Node 150 
               
               
                   
               
            
           
         
       
     
     In the example of the forwarding table shown by Table 1, network node  110 - a  may determine to forward the command to the network node  110 - c . That is, the network node  110 - a  may reference the second and third entries of the forwarding table (e.g., corresponding to the ‘Node’ network node  110 - a ). Because the link metric for network node  110 - b  is higher than the link metric for network node  110 - c  (e.g., 10 versus 1), the network node  110 - a  may determine to forward the command to network node  110 - c . Based on determining a next network node  110 , the network node  110 - a  may select an EP  115  for a quantum entangled channel  125  to utilize. Here, the network node  110 - a  may select one of the EPs  115 - d  establishing a quantum entangled channel  125 - c  between the network node  110 - a  and the network node  110 - c.    
     To forward a command, the network node  110 - a  may perform a BSM operation based on the quantum state determined by the QSR operation (e.g., the quantum state of the source particle  145 ) and the selected EP  115 - d . Thus, the network node  110 - a  may cause the source EP  115 - d  to collapse into a classical state (e.g., the EP  115 - d  may no longer be a quantum particle). The network node  110 - a  may transmit, by the digital information channel  120 - c , the BSM result to network node  110 - c . For example, the network node  110 - a  may forward the command to the network node  110 - c  by the digital information channel  120 - c  including the BSM result, an indication of the destination network node  150 , and an identifier or the EP  115 - d  used to determine the BSM result. When the network node  110 - c  receives the command, the network node  110 - c  may perform similar operations (e.g., a QSR operation, referencing a forwarding table, a BSM operation, and forwarding the command to a network node  110 ) as the network node  110 - a . Thus, the command may be forwarded from one network node  110  to another network node  110  until the network node  110 - c  receives and forwards the command to the destination network node  150 . 
     The destination network node  150  may receive the command by the digital information channel  120 - f  and identify one of the quantum entangled channels  125 - f  associated with the command based on an EP identifier within the command The destination network node  150  may perform a QSR operation (e.g., based on the BSM result and one of the EPs  115 - 1  associated with the quantum entangled channels  125 - f ) to recover the quantum state of the source particle  145  with the destination particle  155 . Thus, the system  100  of network nodes  105 ,  110 , and  150  may enable a communication of the quantum state of the source particle  145  from a source network node  105  and a destination network node  150 . 
       FIG.  2    illustrates an example of a configuration  200  of a network node  210  that supports a quantum Internet router in accordance with various aspects of the present disclosure. The network node  210  may include interfaces for a set of digital information channels  220 . The network node  210  may also include EPs  215  establishing a set of quantum entangled channels. The network node  210  may include QSR circuitry  225 , memory  235 , and BSM circuitry  240 .The configuration  200  may include aspects of the system  100  as described with reference to  FIG.  1   . For example, the network node  210  may be an example of a source network node  105 , a network node  110 , or a destination network node  150 ; the digital information channels  220  may be examples of the digital information channels  120 ; and the EPs  215  may be examples of the EPs  115  as described with reference to  FIG.  1   . 
     The network node  210  may receive EPs  215  for establishing quantum entangled channels between the network node  210  and other network nodes. The network node  210  may receive EP transmissions  230  from a control node (e.g., as described with reference to  FIG.  1   ). The EP transmissions  230  may include an EP  215  and an identifier indicating a pair of EPs  215  and the associated quantum entangled channel between the network node  210  and another network node. For example, each of the EPs  215 - a  may be associated with a pair of EPs forming a quantum entangled channel between the network node  210  and another network node (e.g., a same network node). That is, there may be multiple quantum entangled channels between the network node  210  and the other network node each associated with one of the EPs  215 . Here, the network node  210  may receive the EPs  215 - a  from a control node with an associated identifier indicating that the EPs  215 - a  are one of a pair of EPs for a quantum entangled channel between the network node  210  and the other network node. In the example of network node  210 , there are four quantum entangled channel interfaces associated with the EPs  215 - a ,  215 - b ,  215 - c , and  215 - d.    
     The network node  210  may include digital information channel interfaces for receiving or transmitting information (e.g., commands) by the digital information channels  220 . The network node  210  may have a digital information channel interface associated with each of the sets of EPs  215  (e.g.,  215 - a ,  215 - b ,  215 - c , and  215 - d ). That is, the network node  210  may be configured with four digital channel interfaces for communicating with four different nodes by digital information channels  220 . 
     The network node  210  may receive commands by a digital information channel  220 - a . The command may include a BSM result, an EP pair identifier, and an indication of a destination network node. The network node  210  may identify one of the EPs  215  associated with the command based on an identifier within the command For example, the network node  210  may identify one of the EPs  215 - b  based on the identifier within the command The QSR circuitry  225  of the network node  210  may receive the command and the EP  215  indicated by the identifier within the command (e.g., one of the EPs  215 - b ). Based on the BSM within the command and the received EP  215 , the QSR circuitry  225  may output a quantum particle  255  with a same quantum state as a source particle (e.g., as described with reference to  FIG.  1   ). 
     The network node  210  may reference a forwarding table stored within the memory  235  to determine to which network node to forward the command Here, the network node  210  may be in communication with four network nodes (e.g., associated with each of the sets of EPs  215 ), but in other examples, the network node  210  may be coupled with more network nodes or less network nodes. The forwarding table may indicate a network node associated with one of the sets of EPs  215  based on a destination network node indicated within the command For example, the forwarding table may indicate a network node associated with one of EPs  215 - c . Based on the network node indicated by the forwarding table, the BSM circuitry  240  may perform a BSM operation to generate a BSM result. The BSM circuitry  240  may perform the BSM operation based on the quantum particle  255  and one of the EPs  215  associated with a quantum entangled channel between the network node  210  and a network node indicated by the forwarding table. The network node  210  may forward a command by the digital information channel  220 - b  to the indicated network node, where the command includes the BSM result calculated by the BSM circuitry  240 , an identifier of the EP pair used for the BSM operation, and the indication of the destination network node. 
       FIG.  3    illustrates an example of a process flow  300  that supports a quantum Internet router in accordance with various aspects of the present disclosure. The process flow  300  may include operations performed by a control node  335 , a first network node  310 - a , a second network node  310 - b , and a third network node  310 - c . The control node  335  and network nodes  310  may be examples of a control node and network nodes as described with reference to  FIGS.  1  and  2   . Each of the network nodes  310  may be configured to communicate quantum state information (e.g., qubits) from a source network node to a destination network node. 
     At  305 , the control node  335  may transmit EPs to each of the network nodes  310 . 
     The control node may create multiple pairs of EPs and transmit one EP within a pair of EPs to a first network node  310  and the second EP within the pair of EPs to a second network node  310 , thus establishing a quantum entangled channel between the two network nodes. Thus, at  305 - a , the first network node  310 - a  may receive, from the control node  335 , more than one EP each associated with a pair of EPs that establish a quantum entangled channel between the first network node  310 - a  and the second network node  310 - b . The more than one EP may also include EPs that establish one or more quantum entangled channels between the first network node  310 - a  and the third network node  310 - c . At  305 - a , the first network node  310 - a  may additionally receive a set of identifiers identifying the pairs of EPs. At  305 - b  and  305 - c , the second network node  310 - b  and  310 - c  may also receive more than one EP associated with pairs of EPs for establishing a quantum entangled channel with another network node  310 . 
     At  315 , the second network node  310 - b  may transmit a command to the first network node  310 - a . The command may be transmitted by a digital information channel (e.g., a first digital information channel) and may indicate a destination network node, a BSM associated with a first EP of a pair of EPs establishing a quantum entangled channel between the first network node  310 - a  and the second network node  310 - b . The command may additionally include an identifier of the first pair of EPs. 
     At  320 , the first network node  310 - a  may select, based on the destination network node, a third network node  310 - c . In some cases, selecting the third network node  310 - c  may include the first network node  310 - a  referencing a forwarding table, where the forwarding table indicates the third network node  310 - c  based on the destination network node. 
     At  325 , the first network node  310 - a  may optionally transmit an indication of the command (e.g., received at  315 ) to the control node  335 . In some cases, receiving the command at  315  may decrease a quantity of quantum entangled channels between the first network node  310 - a  and the second network node  310 - b . Here, the first network node  310 - a  may transmit the indication of the command based on the quantity of quantum entangled channels between the first network node  310 - a  and the second network node  310 - b  being less than a threshold quantity of quantum entangled channels. 
     In response to the indication received at  325 , at  330 , the control node  335  may optionally create one or more pairs of EPs and transmit one of the EPs of the pair of EPs to the first network node  310 - a  (e.g., at  330 - a ) and the second network node  310 - b  (e.g., at  330 - b ). 
     At  340 , the first network node  310 - a  may perform a QSR operation based on the BSM measurement (e.g., indicated within the command received at  315 ). The first network node  310 - a  may perform the QSR operation to determine a quantum state of a source particle associated with the command received at  315 . 
     At  345 , the first network node  310 - a  may generate a second BSM result based on the first BSM result (e.g., included within the command received at  315 ) and a second EP of a second pair of EPs that establishes a quantum entangled channel between the first network node  310 - a  and the third network node  310 - c . In some cases, the second BSM result may further be based on the quantum state of the source particle determined based on the QSR operation performed at  340 . 
     At  350 , the first network node  310 - a  may transmit the command by a digital information channel to the third network node  310 - b . The second command may indicate the destination network node and the second BSM result generated at  345 . Additionally, the second command may indicate an identifier of the second pair of EPs that establish the quantum entangled channel between the first network node  310 - a  and the third network node  310 - c.    
       FIG.  4    shows a block diagram  400  of a network node  405  that supports a quantum Internet router in accordance with aspects of the present disclosure. The network node  405  may be an example of aspects of network node as described with reference to  FIGS.  1  through  3   . The network node  405  may include a command receiver  410 , a network node selector  415 , a BSM generator  420 , a command transmitter  425 , a QSR manager  430 , and an EP manager  435 . Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses). 
     The command receiver  410  may receive, from a second network node via a first digital information channel, a first command indicating a destination network node and a first BSM associated with a first EP of a first pair of EPs that establish a first quantum entangled channel between the first network node and the second network node. In some cases, the first network node is different than the destination network node. In some examples, the command receiver  410  may receive, from a fourth network node of the set of network nodes different than the second network node, a third command indicating a second destination network node and a third BSM associated with a third pair of EPs of the one or more pairs of EPs that establish a third quantum entangled channel between the first network node and the fourth network node. 
     The network node selector  415  may select, based on the destination network node, a third network node from a set of network nodes, where the first network node includes one or more EPs each associated with respective ones of one or more pairs of EPs that establish respective quantum entangled channels between the first network node and each network node of the set of network nodes. In some examples, the network node selector  415  may select the third network node is based on the first network node being different than the destination network node. In some cases, the selecting the third network node further includes referencing a forwarding table, where the forwarding table indicates the third network node based on the destination network node. 
     The BSM generator  420  may generate a second BSM based on the first BSM and the first EP and associated with a second EP of a second pair of EPs of the one or more pairs of EPs that establishes a second quantum entangled channel between the first network node and the third network node. 
     The command transmitter  425  may transmit, to the third network node by a second digital information channel, a second command indicating the destination network node and the second BSM. In some cases, the second command further indicates an identifier of the second pair of EPs. 
     The QSR manager  430  may perform, based on the first BSM and the first pair of EPs, a QSR operation to determine a quantum state of a source particle associated with the first command, where generating the second BSM is based on the quantum state of the source particle associated with the first command 
     The EP manager  435  may receive, from a control node, more than one EP each associated with a respective pair of EPs that establishes a quantum entangled channel between the first network node and the second network node, where the more than one EP includes the first EP. In some instances, the EP manager  435  may additionally receive, from the control node, a set of identifiers identifying the respective pairs of EPs, where the first command further includes a first identifier of the set of identifiers identifying the first pair of EPs. In some examples, the EP manager  435  may transmit, to a control node, an indication of receiving the first command indicating the first BSM associated with the first pair of EPs that establish the first quantum entangled channel between the first network node and the second network node. In some instances, the EP manager  435  may receive, from the control node, a third EP associated with a third pair of EPs that establishes a third entangled channel between the first network node and the second network node. In some examples, receiving the first command indicating the first BSM associated with the first pair of EPs that establish the first quantum entangled channel between the first network node and the second network node decreases a quantity of quantum entangled channels between the first network node and the second network node by one. The EP manager  435  may transmit the indication is based on the quantity of quantum entangled channels between the first network node and the second network node being less than a threshold quantity of entangled channels between the first network node and the second network node based on decreasing the quantity of quantum entangled channels between the first network node and the second network node by one. 
       FIG.  5    shows a flowchart illustrating a method  500  that supports a quantum Internet router in accordance with aspects of the present disclosure. The operations of method  500  may be implemented by a first network node or its components as described herein. For example, the operations of method  500  may be performed by a network node as described with reference to  FIGS.  1  through  4   . Additionally or alternatively, the operations of method  500  may be performed by the memory within the network node, the BSM circuitry, or the QSR circuitry within the network node as described with reference to  FIG.  2   . In some examples, a first network node may execute a set of instructions to control the functional elements of the first network node to perform the described functions. Additionally or alternatively, a first network node may perform aspects of the described functions using special-purpose hardware. 
     At  505 , the first network node may receive, from a second network node via a first digital information channel, a first command indicating a destination network node and a first BSM associated with a first EP of a first pair of EPs that establish a first quantum entangled channel between the first network node and the second network node. The operations of  505  may be performed according to the methods described herein. In some examples, aspects of the operations of  505  may be performed by a command receiver as described with reference to  FIG.  4   . 
     At  510 , the first network node may select, based on the destination network node, a third network node from a set of network nodes, where the first network node includes one or more EPs each associated with respective ones of one or more pairs of EPs that establish respective quantum entangled channels between the first network node and each network node of the set of network nodes. The operations of  510  may be performed according to the methods described herein. In some examples, aspects of the operations of  510  may be performed by a network node selector as described with reference to  FIG.  4   . 
     At  515 , the first network node may perform, based on the first BSM and the first pair of EPs, a QSR operation to determine a quantum state of a source particle associated with the first command, where generating the second BSM is based on the quantum state of the source particle associated with the first command. The operations of  515  may be performed according to the methods described herein. In some examples, aspects of the operations of  515  may be performed by a QSR manager as described with reference to FIG. 
       4 . 
     At  520 , the first network node may generate a second BSM based on the first BSM and the first EP and associated with a second EP of a second pair of EPs of the one or more pairs of EPs that establishes a second quantum entangled channel between the first network node and the third network node. The operations of  515  may be performed according to the methods described herein. In some examples, aspects of the operations of  515  may be performed by a BSM generator as described with reference to  FIG.  4   . 
     At  525 , the first network node may transmit, to the third network node by a second digital information channel, a second command indicating the destination network node and the second BSM. The operations of  520  may be performed according to the methods described herein. In some examples, aspects of the operations of  520  may be performed by a command transmitter as described with reference to  FIG.  4   . 
     It should be noted that the methods described herein describe possible implementations, and that the operations and the steps may be rearranged or otherwise modified and that other implementations are possible. Further, aspects from two or more of the methods may be combined. 
     The various illustrative blocks and modules described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a digital signal processor (DSP), an ASIC, an FPGA, or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration). 
     The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of the disclosure and appended claims. For example, due to the nature of software, functions described herein can be implemented using software executed by a processor, hardware, firmware, hardwiring, or combinations of any of these. Features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations. 
     Computer-readable media includes both non-transitory computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A non-transitory storage medium may be any available medium that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, non-transitory computer-readable media may include random-access memory (RAM), read-only memory (ROM), electrically erasable programmable ROM (EEPROM), flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, include CD, laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media. 
     As used herein, including in the claims, “or” as used in a list of items (e.g., a list of items prefaced by a phrase such as “at least one of” or “one or more of”) indicates an inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). Also, as used herein, the phrase “based on” shall not be construed as a reference to a closed set of conditions. For example, an exemplary step that is described as “based on condition A” may be based on both a condition A and a condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase “based on” shall be construed in the same manner as the phrase “based at least in part on.” 
     In the appended figures, similar components or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If just the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label, or other subsequent reference label. 
     The description set forth herein, in connection with the appended drawings, describes example configurations and does not represent all the examples that may be implemented or that are within the scope of the claims. The term “exemplary” used herein means “serving as an example, instance, or illustration,” and not “preferred” or “advantageous over other examples.” The detailed description includes specific details for the purpose of providing an understanding of the described techniques. These techniques, however, may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples. 
     The description herein is provided to enable a person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not limited to the examples and designs described herein, but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.