QUANTUM LIDAR SYSTEM

One example includes a quantum lidar system. The system includes a beam generator configured to generate a signal beam and an idler beam and a beam combiner configured to generate a combined optical beam comprising the signal beam and the idler beam. The system also includes a lidar transmitter configured to transmit the combined optical beam to a target and a lidar receiver configured to receive the combined optical beam and a reflected beam of the combined optical beam reflected from the target to generate lidar data associated with the target.

TECHNICAL FIELD

The present invention relates generally to lidar systems, and specifically to a quantum lidar system.

BACKGROUND

Lidar is a type of sensor that can provide range-finding and/or imaging based on a laser. As an example, a lidar system can determining ranges (variable distance) by targeting an object with a laser and measuring the time for the reflected light to return to the receiver. A lidar system can also be used to create digital three-dimensional images of areas on terrestrial surfaces, on the ocean floor, and/or structures (e.g., buildings) thereon due to differences in laser return times and by varying laser wavelengths. A quantum lidar system can typically implement a nonlinear device to degeneratively create a signal beam and an idler beam from a single optical pump beam, such that the signal beam provided to the target and the idler beam provided to a local reference can be used to generate lidar data associated with the target.

SUMMARY

One example includes a quantum lidar system. The system includes a beam generator configured to generate a signal beam and an idler beam and a beam combiner configured to generate a combined optical beam comprising the signal beam and the idler beam. The system also includes a lidar transmitter configured to transmit the combined optical beam to a target and a lidar receiver configured to receive the combined optical beam and a reflected beam of the combined optical beam reflected from the target to generate lidar data associated with the target.

Another example includes a method for generating lidar data associated with a target. The method includes providing the combined optical beam to a lidar receiver. The method also includes transmitting the combined optical beam to the target, and receiving a reflected beam of the combined optical beam reflected from the target at the lidar receiver to generate the lidar data associated with the target based on the combined optical beam and the reflected beam.

Another example includes a quantum lidar system. The system includes a beam generator configured to generate a signal beam and an idler beam and a beam combiner configured to generate a combined optical beam comprising the signal beam and the idler beam. The signal beam and the idler beam can have unequal frequencies. The system also includes a lidar transmitter configured to transmit the combined optical beam to a target. The system further includes a lidar receiver. The lidar receiver includes a local detector configured to receive the combined optical beam and to generate a first detection signal associated with the combined optical beam. The lidar receiver also includes a target detector configured to receive a reflected beam of the combined optical beam reflected from the target and to generate a second detection signal associated with the reflected beam. The lidar receiver further includes a lidar processor configured to generate lidar data associated with the target based on the first and second detection signals.

DETAILED DESCRIPTION

The present invention relates generally to lidar systems, and specifically to a quantum lidar system. The quantum lidar system can be implemented for any of a variety of applications for range-finding and/or imaging. The quantum lidar system includes a beam generator that is configured to generate a signal beam and an idler beam. As an example, the signal and idler beams can be degeneratively created based on providing an optical pump beam through a nonlinear device. As an example, the nonlinear device can be a spontaneous parametric downconverter (SPDC) device, such as to generate the signal beam and the idler beams as having different frequencies. The quantum lidar system also includes a beam combiner that is configured to combine the signal beam and the idler beam to generate a combined optical beam. The beam combiner can be configured as a set of optics that can generate the combined optical beam and provide the combined optical beam to a lidar transmitter and to a lidar receiver.

The lidar transmitter can be configured to provide the combined optical beam to a target. The combined optical beam can be reflected from the target to provide a reflected beam. The lidar receiver can receive both the combined optical beam (e.g., from the beam combiner) and the reflected beam and can generate lidar data associated with the target based on the combined optical beam and the reflected beam. For example, the lidar receiver can include a lidar processor that can implement a delayed choice temporal convolution algorithm to generate the lidar data. Based on the quantum entanglement of the signal and idler beams in the combined optical beam provided to both the target and the lidar receiver, the lidar processor can greatly increase a signal-to-noise ratio (SNR) of the resultant lidar data based on determining a convolution peak of one of the signal and idler beams in the combined optical signal provided to the lidar receiver and the other of the signal and idler beams in the reflected beam provided to the lidar receiver.

FIG.1illustrates an example block diagram of a quantum lidar system100. The quantum lidar system100can be implemented in any of a variety of range-finding and/or imaging applications with respect to a target102. The target102can correspond to geographic features (e.g., terrestrial, underwater, and/or surfaces of other celestial bodies) or to man-made structures, such as buildings or vehicles. Thus, the quantum lidar system100can be configured to determine a range to the target102and/or generate image data associated with the target102.

The quantum lidar system100includes a beam generator104and a beam combiner106. The beam generator104is configured to generate a signal beam and an idler beam that can be implemented in a quantum entangled beam (e.g., via a nonlinear device). The beam combiner106is thus configured to combine the signal beam and the idler beam to generate the quantum entangled beam, described hereinafter as a “combined optical beam”. The combined optical beam, demonstrated in the example ofFIG.1as a beam OPTCMBD, can therefore include both the signal beam and the idler beam having a common wavefront. As an example, the beam combiner106can include a variety of different types of optical devices to combine the signal beam and the idler beam. As described herein, the beam combiner106can generate the combined optical beam OPTCMBDsuch that the signal beam and the idler beam have a single photon entanglement.

The beam combiner106can provide the combined optical beam OPTCMBDto a lidar transmitter108and a lidar receiver110. The lidar transmitter108is therefore configured to illuminate the target102with the combined optical beam OPTCMBD. The combined optical beam OPTCMBDis thus reflected from the target102and provided back to quantum lidar system100as a reflected beam OPTRFLto be received by the lidar receiver110. The lidar receiver110thus receives both the combined optical beam OPTCMBDand the reflected beam OPTRFL, such that the lidar receiver110is configured to generate lidar data associated with the target102based on the combined optical beam OPTCMBDand the reflected beam OPTRFL. As an example, the lidar receiver110can include a lidar processor that is configured to implement a temporal convolution algorithm on the combined optical beam OPTCMBDand the reflected beam OPTRFLto generate the lidar data associated with the target102. The temporal convolution algorithm can be a delayed choice detection algorithm, such that the temporal convolution algorithm can be implemented at a time after receipt of the reflected beam OPTRFL.

As an example, the lidar receiver110can include a local detector that is configured to monitor the combined optical beam OPTCMBDand a target detector that is configured to monitor the reflected beam OPTRFL. Because the combined optical beam OPTCMBDincludes both the signal beam and the idler beam, the reflected beam OPTRFLlikewise includes the signal beam and the idler beam reflected back from the target102. Therefore, the local detector of the lidar receiver110can agnostically detect one of the signal beam and the idler beam in the combined optical beam OPTCMBD, and the target detector of the lidar receiver can agnostically detect the other one of the signal beam and the idler beam in the reflected beam OPTRFL. As a result, the lidar processor can implement the temporal convolution algorithm in a manner that increases signal-to-noise ratio (SNR) for a stronger correlation between the combined optical beam OPTCMBDand the reflected beam OPTRFL, and which obviates the need for a quantum memory. As a result, the quantum lidar system100can have a simpler design without the quantum memory, and can provide for more accurate lidar data associated with the target102.

The quantum lidar system200includes a beam generator202. The beam generator202is configured to generate a signal beam OPTSGNLand an idler beam OPTIDLRthat can be implemented in a quantum entangled beam. As an example, the signal beam OPTSGNLand the idler beam OPTIDLRcan be generated based on a parametric degeneration process from an optical pump beam provided through a nonlinear device. For example, the beam generator202can include a spontaneous parametric downconverter (SPDC) to generate the signal beam OPTSGNLand the idler beam OPTIDLRfrom the optical pump beam. Therefore, the signal beam OPTSGNLand the idler beam OPTIDLRcan be generated to have unequal frequencies. Therefore, the signal beam OPTSGNLand the idler beam OPTIDLRcan be separately detected, as described in greater detail herein.

The quantum lidar system200also includes a beam combiner204that is configured to combine the signal beam OPTSGNLand the idler beam OPTIDLRto generate the combined optical beam OPTCMBD. The combined optical beam OPTCMBDcan therefore include both the signal beam OPTSGNLand the idler beam OPTIDLRhaving a common wavefront. As an example, the beam combiner204can include a variety of different types of optical devices to combine the signal beam and the idler beam. As another example, the beam combiner204can be combined with the beam generator202, such that the beam generator202and the beam combiner204can include a set of optics that operate together to generate the combined optical beam OPTCMBDthat includes the signal beam OPTSGNLand the idler beam OPTIDLR. As an example, the beam combiner204can generate the combined optical beam OPTCMBDsuch that the signal beam OPTSGNLand the idler beam OPTIDLRhave a single photon entanglement.

The beam combiner204can provide the combined optical beam OPTCMBDto a lidar transmitter206and a lidar receiver208(e.g., via optics). The lidar transmitter206is therefore configured to illuminate a target (e.g., the target102) with the combined optical beam OPTCMBD. The combined optical beam OPTCMBDis thus reflected from the target and provided back to quantum lidar system200as a reflected beam OPTRFLto be received by the lidar receiver208. The lidar receiver208thus receives both the combined optical beam OPTCMBDand the reflected beam OPTRFL, such that the lidar receiver208is configured to generate lidar data associated with the target based on the combined optical beam OPTCMBDand the reflected beam OPTRFL. As an example, the lidar receiver208can include a lidar processor that is configured to implement a temporal convolution algorithm on the combined optical beam OPTCMBDand the reflected beam OPTRFLto generate the lidar data associated with the target. The temporal convolution algorithm can be a delayed choice detection algorithm, such that the temporal convolution algorithm can be implemented at a time after receipt of the reflected beam OPTRFL.

FIG.3illustrates an example block diagram of a beam generator300. The beam generator300can correspond to the beam generators104and202of the respective examples ofFIGS.1and2. Therefore reference is to be made to the examples ofFIGS.1and2in the following description of the example ofFIG.3.

The beam generator300includes a beam source302that is configured to generate an optical pump beam OPTPMP. The beam source302can be a laser, waveguide, optical fiber, or other component to provide the optical pump beam OPTPMP. The beam generator300also includes an SPDC304that is configured to degeneratively create the signal beam OPTSGNLand the idler beam OPTIDLRfrom the optical pump beam OPTPMP. For example, the signal beam OPTSGNLand the idler beam OPTIDLRcan have unequal frequencies. While the example ofFIG.3demonstrates that the nonlinear device that generates the signal beam OPTSGNLand the idler beam OPTIDLRis the SPDC304, other types of nonlinear devices could be used instead. Additionally, as one example, the optical pump beam OPTPMPcan be provided in a single pass through the SPDC304to provide for a single photon entanglement of the signal beam OPTSGNLand the idler beam OPTIDLR.

FIG.4illustrates an example block diagram of a lidar receiver400. The lidar receiver400can correspond to the lidar receiver110and the lidar receiver208in the respective examples ofFIGS.1and2. Therefore, reference is to be made to the examples ofFIGS.1and2in the following description of the example ofFIG.4.

The lidar receiver400includes a local detector402. The local detector402is configured to receive the combined optical beam OPTCMBDfrom the beam combiner (e.g., via optics). The local detector402includes a local photon counter404that is configured to monitor photons associated with either the signal beam OPTSGNLand the idler beam OPTIDLRof the combined optical beam OPTCMBD. As an example, the local photon counter404can be tuned to the frequencies of the signal beam OPTSGNLand the idler beam OPTIDLR, such that the local photon counter404can agnostically identify one of the signal beam OPTSGNLand the idler beam OPTIDLRin the combined optical beam OPTCMBD.

The lidar receiver400also includes a target detector406. The target detector406is configured to receive the reflected beam OPTRFLreflected back from the target (e.g., the target102). The target detector406includes a target photon counter408that is configured to monitor photons associated with either the signal beam OPTSGNLand the idler beam OPTIDLRportions of the reflected beam OPTRFL. As an example, the target photon counter408can be tuned to the frequencies of the signal beam OPTSGNLand the idler beam OPTIDLR, such that the target photon counter408can agnostically identify one of the signal beam OPTSGNLand the idler beam OPTIDLRin the reflected beam OPTRFL. The one of the signal beam OPTSGNLand the idler beam OPTIDLRthat is detected by the target detector406is the opposite of the signal beam OPTSGNLand the idler beam OPTIDLRthat is detected by the local detector402. Therefore, the lidar receiver400can find a correlation between one of the signal beam OPTSGNLand the idler beam OPTIDLRin one of the combined optical beam OPTCMBDand the reflected beam OPTRFLand the other of the signal beam OPTSGNLand the idler beam OPTIDLRin the other of the combined optical beam OPTCMBDand the reflected beam OPTRFL. For example, the quantum lidar system can exhibit a range accuracy of 0.5*C*ΔT, where C is the speed of light and ΔT is the response time of the local and target detectors402and406.

In the example ofFIG.4, the local detector402is configured to generate a first detection signal DET1that corresponds to the respective one of the signal beam OPTSGNLand the idler beam OPTIDLRin the combined optical beam OPTCMBD. Similarly, the target detector406is configured to generate a second detection signal DET2that corresponds to the respective other one of the signal beam OPTSGNLand the idler beam OPTIDLRin the reflected beam OPTRFL. The detection signals DET1and DET2are provided to a lidar processor410that is configured to generate the lidar data associated with the target based on the detection signals DET1and DET2.

As an example, the lidar processor410can implement a delayed choice temporal convolution algorithm on the detection signals DET1and DET2to generate the lidar data. For example, the lidar processor410can provide temporal synchronization of the local detector402and the target detector406over a period of time and store the time bins corresponding to the detection signals DET1and DET2to implement a delayed choice processing of the detection signals DET1and DET2. The lidar processor410can then convolve the detection signals DET1and DET2with a variable time delay, such that sweeping the time delay across the range gate can provide a convolution peak corresponding to the time bins of maximum correlation between the detection signals DET1and DET2. The time offset that corresponds to the convolution peak can thus correspond to the range to the target.

As described herein, the combined optical beam OPTCMBDthat is provided to the local detector402includes both the signal beam OPTSGNLand the idler beam OPTIDLR, and the combined optical beam OPTCMBDthat is reflected from the target back to the target detector406likewise includes both the signal beam OPTSGNLand the idler beam OPTIDLR. Based on implementing the quantized representation of the electric fields for the photons of the signal beam OPTSGNLand the idler beam OPTIDLR, and by calculating the correlation between the combined optical beam OPTCMBDand the reflected beam OPTRFL, only the entangled photons contribute to the convolution. Thus, only one of the signal beam OPTSGNLand the idler beam OPTIDLRof the combined optical beam OPTCMBDand the other one of the signal beam OPTSGNLand the idler beam OPTIDLRof the reflected beam OPTRFLcontribute to the convolution, as determined at the local detector402and the target detector406. Accordingly, the lidar processor410can determine the lidar data at a significantly higher SNR relative to typical lidar processing algorithms. Furthermore, because the time synchronized detections of the combined optical beam OPTCMBDand the reflected beam OPTRFLare performed separately in the delayed choice manner, the lidar receiver400does not need a quantum memory to determine the lidar data associated with the target.

In view of the foregoing structural and functional features described above, a methodology in accordance with various aspects of the disclosure will be better appreciated with reference toFIG.5. It is to be understood and appreciated that the method ofFIG.5is not limited by the illustrated order, as some aspects could, in accordance with the present disclosure, occur in different orders and/or concurrently with other aspects from that shown and described herein. Moreover, not all illustrated features may be required to implement a methodology in accordance with an aspect of the present examples.

FIG.5illustrates an example of a method500for generating lidar data associated with a target (e.g., the target102). At502, a combined optical beam (e.g., the combined optical beam OPTCMBD) is provided to a lidar receiver (e.g., the lidar receiver110). The combined optical beam includes a signal beam and an idler beam. At504, the combined optical beam is transmitted to the target. At506, a reflected beam (e.g., the reflected beam OPTRFL) of the combined optical beam reflected from the target is received at the lidar receiver to generate the lidar data associated with the target based on the combined optical beam and the reflected beam.