Patent ID: 12235304

DETAILED DESCRIPTION

The present invention provides a radiofrequency (RF) receiver that has plural quantum-sensor detection channels tuned to different frequencies to achieve relatively wideband detection in the aggregate. Each channel contains a population of quantum particles (e.g., atoms or polyatomic molecules) excited to Rydberg states. Each channel tracks the RF intensity for its respective narrow frequency band by tracking absorption of a probe beam that has passed through the quantum particles.

In “single-cell multi-channel” embodiments, plural channels extend through the same atom-vapor cell so that there is no solid barrier between the quantum-particle populations; in other embodiments, each channel has its own cell so that the quantum-particle populations are hermetically sealed from each other. However, in some multi-channel cells, quantum-particle populations can be concentrated along respective channels, e.g., using optical, magnetic, or magneto-optical confinement and/or traps. The single-cell design is more compact and more robust than a system assembled using single-channel cells. Also, cell failure is more readily detected since multiple channels are affected concurrently. Both designs offer improved performance for frequency hopping and other multi-frequency transmission environments.

A single-cell dual-channel quantum-sensor receiver100is shown schematically inFIG.1including a hermetically sealed atom-vapor cell102in the form of a rectangular parallelepiped. Additional views of cell102are provided inFIGS.2A and2B. Cell102contains a vapor of rubidium 87 (87Ru) atoms; other embodiments employ other atoms or molecules. Channels104and106are defined through cell102and differentiated by their respective electric fields.

These electric fields are controlled by an electric source108via respective electrodes110(for channel104) and112(for channel106). Electric source108provides a respective AC voltage with a respective DC offset to electrodes110and112. The respective DC offsets are chosen to tune, using a Stark effect, the respective channels104and106to respective frequencies f1 and f2. The respective AC frequencies f1 and f2 are used to demodulate the carriers for channels104and106, respectively.

A laser system114provides probe beams116and118and coupling beams120that are used to excite the 87Ru atoms to a Rydberg state |60S7/2; in other embodiments, different Rydberg states are reached. As shown in the energy-level diagram ofFIG.3, a λp=780 nm probe can transition an 87Ru atom from a 1551/2) ground state to a |5P3/2) excited state. A λd=776 nm first coupling (aka “dressing”) beam can transition an 87Ru atom from the |5P3/2excited state to an |5D5/2excited states. A Ac=1257 nm second coupling beam can transition an 87Ru atom from the |5D5/2excited state to the |60S7/2Rydberg state.

In the absence of an RF wavefront, the probe beam is absorbed to some extent as it passes through the 87Ru atoms in the states listed above. However, in the presence of a 380 MHz (78.893 cm) radiofrequency wavefront120, atoms in the |60S7/2Rydberg state can transition to a |60G9/2Rydberg state from which they cannot readily return to the |5S1/2ground state required for the probe beam to be absorbed; other frequencies can be used depending on channel tuning. Accordingly, the absorption peak that characterizes the absence of an RF field is reduced in the presence of the RF field of the proper frequency. Photodetectors124and126(FIG.1) respectively track absorption of probes116and118so that the intensity of the pertinent RF field can be determined. Signal processor128then converts the photodetector readouts for an application specific use.

A four-channel atom-vapor cell400is represented inFIG.4including a hermetically sealed glass structure with opposing walls402and404. Indium-titanium oxide (ITO) electrodes431,432,441, and442are formed on the inner surfaces of opposing walls402and404, while a common ground electrode451extends longitudinally through cell400. These electrodes allow independent tuning for channels411,412,421, and422. Note that the channels in cell400are arranged in a two-dimensional array, whereas the channels in receiver system100(FIG.1) are arranged in a one-dimensional array. Other embodiments use transparent conductive oxides (TCOs) other than ITO.

FIGS.5A and5Brepresent a one-cell per channel multi-channel system500. The cells511,512,521. . . are arranged in an n-by-m two-dimensional array, where n and m are integers. Each cell511,512,521and so on, includes a single respective channel531,532,541. . . .

A multi-channel quantum-sensing radiofrequency receiver process600, flow-charted inFIG.6, begins at601with forming or obtaining a vapor cell of quantum particles, e.g., atoms or polyatomic molecules, with low-conductivity electrodes on the cell walls to define channels. Some embodiments include a single multi-channel cell, while other embodiments can include plural cells which can include single- and/or multi-channel cells.

Each cell can contain a molecular entity capable of assuming a superposition of Rydberg states. At602, the quantum particles are excited to a first Rydberg state using a probe and one or more coupling laser beams for a n-photon transition, where n≥2. At603, the channels are tuned to respective relatively narrow frequency bands by applying electrical potentials across electrodes. More specifically, the RF frequency required to transition between the first Rydberg state and a second Rydberg state can be adjusted using a Stark effect due to applied electric fields. The tuning is effected by a direct current (DC) potential. However, an alternating (AC) potential can be applied to demodulate an RF signal.

At604, for each channel, the absorption of the respective probe beam by the quantum particles is tracked, e.g., using a photodetector positioned to detect the probe beam after it has passed through the quantum particles. An absorption peak is maximal in the absence of an RF field at the frequency to which the channel is tuned and decreases with RF intensity in the tuned frequency. Thus, tracking the absorptions of probe beams in the channels gives, at605, a parallel readout of RF intensity in each single-channel frequency range within the wider frequency range of the receiver system.

The |60S7/2→|60G9/2transition between Rydberg states provides for detection of frequencies near the lower limit of UHF frequencies and in the range of 380±0.2 MHz. Applying electric fields to modify the transition to differentially tune channels can extend the range to 380±2.0 MHz. Further bandwidth broadening can be achieved using different Rydberg transitions associated with the same or a different quantum-particle species. For example, one Rydberg transition can be for 87Ru and another for 133Cs. Likewise, center frequencies higher in the UHF range and frequencies in the VHF range can be tracked by corresponding selections of Rydberg transitions.

Herein, a “system” is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A “process” is a system in which the elements are actions. “Quantum” is an adjective characterizing a system as exhibiting or using quantum-mechanical phenomena such as eigenstates (solutions to Schrodinger's time dependent or time independent Wave Equation), superposition, and entanglement. Quantum states are eigenstates and superpositions of eigenstates. Herein, “quantum particle” is synonymous with “molecular entity.” A “molecular entity” is “any constitutionally or isotopically distinct atom, molecule, ion, ion pair, radical, radical ion, complex, conformer, etc., identifiable as a separately distinguishable entity”. “Quantum-sensing” means sensing using quantum phenomena such as superpositions of Rydberg states.

The invention can be implemented in numerous ways, including as a process; an apparatus; a system; a composition of matter; a computer program product embodied on a computer readable storage medium; and/or a processor, such as a processor configured to execute instructions stored on and/or provided by a memory coupled to the processor. In this specification, these implementations, or any other form that the invention may take, may be referred to as techniques. In general, the order of the steps of disclosed processes may be altered within the scope of the invention. Unless stated otherwise, a component such as a processor or a memory described as being configured to perform a task may be implemented as a general component that is temporarily configured to perform the task at a given time or a specific component that is manufactured to perform the task. As used herein, the term ‘processor’ refers to one or more devices, circuits, and/or processing cores configured to process data, such as computer program instructions.

A detailed description of one or more embodiments of the invention is provided herein along with accompanying figures that illustrate the principles of the invention. The invention is described in connection with such embodiments, but the invention is not limited to any embodiment. The scope of the invention is limited only by the claims and the invention encompasses numerous alternatives, modifications and equivalents. Numerous specific details are set forth in the following description in order to provide a thorough understanding of the invention. These details are provided for the purpose of example and the invention may be practiced according to the claims without some or all of these specific details. For the purpose of clarity, technical material that is known in the technical fields related to the invention has not been described in detail so that the invention is not unnecessarily obscured.

Herein, art labelled “prior art, if any, is admitted prior art; art not labelled “prior art”, if any, is not admitted prior art. The illustrated embodiments, variations thereupon and modifications thereto are provided for by the present invention, the scope of which is defined by the accompanying claims.