Application of superconducting devices to mix surface acoustic waves and microwave signals.

Abstract

To provide a superconducting device implemented with a surface acoustic wave resonator and a superconducting microwave resonator that are coupled to a Josephson ring modulator, and methods of applications thereof.SOLUTION: A method comprises: receiving, by a microwave Josephson mixer and from a superconducting surface acoustic wave resonator of a superconducting device, a surface acoustic wave signal that comprises one or more phonons that resonate at a first frequency; receiving, by the microwave Josephson mixer and from a superconducting microwave resonator of the superconducting device, a microwave signal that comprises one or more photons that can resonate at a second frequency; and mixing, by the microwave Josephson mixer, the surface acoustic wave signal and the microwave signal on the basis of a microwave control signal received from a microwave source operatively coupled to the microwave Josephson mixer.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to the application of superconducting devices to mix surface acoustic waves and microwave signals. [Background technology]

[0002] In quantum circuits, a Josephson ring modulator is coupled to two superconducting microwave resonators, and three-wave mixing is performed between the differential modes supported by the two resonators and a non-resonant common drive supplied to the Josephson ring modulator. Due to the coupling of the Josephson ring modulator to two superconducting microwave resonators, this device has limited frequency selection for the differential modes, which can lead to one or more problems. For example, connecting the Josephson ring modulator to a low-frequency transmission line resonator can pose various challenges, such as occupying a large area (e.g., a large footprint). Another issue is the relatively large linear inductance associated with the low-resonant frequency transmission line compared to the inductance of the Josephson ring modulator. This can result in a significant reduction in the engagement ratio, thereby requiring a very high external quality factor (Q) of the resonators for operation. However, a high external Q of the resonator is undesirable because it can result in an extremely narrow dynamic bandwidth, thereby significantly limiting the availability and practicality of the device.

[0003] Furthermore, coupling Josephson ring modulators to low-frequency lumped-element resonators can require the use of large lumped capacitances and large lumped inductances. Large lumped capacitances and inductances are difficult to realize in practice. Large capacitances can have significant losses (degrading the internal Q of the device), potentially resulting in the loss of a significant portion of the quantum signal. Large geometric inductances typically suffer from parasitic capacitances that limit their usefulness. Large mechanical inductances typically rely on unconventional microscopic superconductors, which are difficult to fabricate and integrate. Summary of the Invention

[0004] The following presents a summary of the invention in order to provide a basic understanding of one or more embodiments of the invention. This summary is not intended to identify key or critical elements or to delineate the scope of particular embodiments or the claims. Its sole purpose is to present concepts in a simplified form as a prelude to the more detailed description that is presented later. Described herein, in one or more embodiments, are devices, systems, methods, apparatus, and / or computer program products that mix surface acoustic waves and microwave signals, facilitate lossless frequency conversion between surface acoustic waves and microwave signals, provide a non-degenerate parametric Josephson amplifier for surface acoustic waves and microwave signals, and create entangled states between phonon and photon modes.

[0005] According to one embodiment, a method may include receiving, by a microwave Josephson mixer, a surface acoustic wave signal including one or more phonons resonating at a first frequency from a superconducting surface acoustic wave resonator of a superconducting device. The method may also include receiving, by the microwave Josephson mixer, a microwave signal including one or more photons resonating at a second frequency from a superconducting microwave resonator of the superconducting device. The method may also include mixing, by the microwave Josephson mixer, the surface acoustic wave signal and a microwave signal based on a microwave control signal received from a microwave source operably coupled to the microwave Josephson mixer. An advantage of such a method is that it can perform dissipative three-wave mixing and amplification between a low microwave frequency of the superconducting surface acoustic wave resonator and a high microwave frequency of the superconducting microwave resonator. Another advantage is that it can unitarily convert quantum information carried by the surface acoustic wave signal to a microwave signal or vice versa (e.g., energy and phase coherence of the quantum signal are preserved). This quantum operation can also be controlled and enabled by a separate microwave control signal received by the device (called a pump or pump device).

[0006] In some implementations, the method may include transferring quantum information from a superconducting surface acoustic wave resonator to a superconducting microwave resonator (or from the superconducting microwave resonator to the surface acoustic wave resonator, or in both directions) by a microwave Josephson mixer based on application of a pump drive applied at a frequency difference between a microwave signal and a surface acoustic wave signal. An advantage of such a method is that a microwave control signal can be used to select the mode in which information is exchanged or converted.

[0007] In some implementations, the method may advantageously include severing a connection or interaction between the superconducting surface acoustic wave resonator and the superconducting microwave resonator based on a determination that the microwave Josephson mixer will cease mixing of the surface acoustic wave signal and the microwave signal. The method may also include re-enabling a connection or interaction between the superconducting surface acoustic wave resonator and the superconducting microwave resonator based on a determination that the microwave Josephson mixer will resume mixing of the surface acoustic wave signal and the microwave signal. An advantage of such a method is that the microwave Josephson mixer can control the transfer of information between the surface acoustic wave signal and the microwave signal.

[0008] According to some implementations, the method may include transferring, by a microwave Josephson mixer, a first portion of quantum information between the superconducting surface acoustic wave resonator and the superconducting microwave resonator based on a first power of a microwave control signal. The method may also include transferring, by the microwave Josephson mixer, a second portion of quantum information between the superconducting surface acoustic wave resonator and the superconducting microwave resonator based on a second power of the microwave control signal. An advantage of such a method is that the amount of information transferred can be controlled by the microwave Josephson mixer and the power of the microwave control signal.

[0009] Another embodiment may include receiving, at a frequency converter, a surface acoustic wave signal from a superconducting surface acoustic wave resonator, the surface acoustic wave signal including one or more phonons resonating at a first frequency. The method may also include receiving, at the frequency converter, a microwave signal from a superconducting microwave resonator, the microwave signal including one or more photons resonating at a second frequency. The method may also include performing, by the frequency converter, a lossless frequency conversion between the first information of the superconducting surface acoustic wave resonator and the second information of the superconducting microwave resonator based on a pump signal received from a microwave source. An advantage of such a method is that the conversion between the surface acoustic wave and the microwave signal is a lossless frequency conversion.

[0010] According to some implementations, the method may include mapping, by a frequency converter, a propagating high-frequency signal to a phonon mode in the superconducting surface acoustic wave resonator. The method may also include upconverting, by the frequency converter, the phonon mode to a photon mode in the superconducting microwave resonator by applying a microwave control signal (e.g., a pump) of a defined frequency. The upconversion of the phonon mode may be enabled by a lossless three-wave mixing interaction. The upconverted microwave signal propagates upon exiting the superconducting microwave resonator. An advantage of such a method is that a propagating phonon mode or a low-frequency microwave signal may be upconverted to a propagating photon mode (e.g., a high-frequency microwave mode) by a lossless three-wave mixing interaction.

[0011] Alternatively, the method may include mapping a propagating microwave signal to a photon mode in a superconducting microwave resonator by a frequency converter. The method may also include downconverting the photon mode to a phonon mode in a superconducting surface acoustic wave resonator by applying a microwave control signal (e.g., a pump) of a defined frequency by the frequency converter. The photon mode downconversion may be enabled by a lossless three-wave mixing interaction. Furthermore, the downconverted surface acoustic wave signal may propagate upon exiting the superconducting surface acoustic wave resonator. An advantage of such a method is that a propagating photon mode (e.g., a high-frequency microwave mode) may be downconverted to a propagating phonon mode or a low-frequency microwave mode by a lossless three-wave mixing interaction.

[0012] According to another embodiment, a method may include amplifying, by a Josephson parametric amplifier, a first quadrature phase of a surface acoustic wave signal entering a first port of the device and a second quadrature phase of a microwave signal entering a second port of the device. The method may also include outputting, by the Josephson parametric amplifier, via an output port, a first amplified signal including the first reflected signal and the frequency-converted first transmitted signal, and a second amplified signal including the second reflected signal and the frequency-converted second transmitted signal. An advantage of such a method is that it can function as a phase-preserving quantum-limited amplifier for low-frequency microwave signals and high-frequency microwave signals.

[0013] In another embodiment, a method is provided that may include inputting, by an entanglement component, a first input signal having a first frequency to a superconducting surface acoustic wave resonator. A first qubit is operably coupled to the entanglement component via a superconducting surface acoustic wave resonator. The method may also include inputting, by the entanglement component, a second input signal having a second frequency to the superconducting microwave resonator. A second qubit is operably coupled to the entanglement component via a superconducting microwave resonator. The method may also include outputting, by the entanglement component, an output signal including an amplified superposition of input fields entering the superconducting surface acoustic wave resonator and the superconducting microwave resonator. An advantage of such a method is that entanglement between phonon and photon modes may exist.

[0014] Yet another embodiment relates to a superconducting device that may include a first superconducting qubit capacitively coupled to a superconducting surface acoustic wave resonator and a second superconducting qubit capacitively coupled to a superconducting microwave resonator. The superconducting device may also include a Josephson ring modulator coupled to the superconducting surface acoustic wave resonator and the superconducting microwave resonator. An advantage of such a superconducting device is that it can operate as a non-degenerate amplifier, allowing entanglement between the qubits to be induced by entanglement between phonons supported by the superconducting surface acoustic wave resonator and photons supported by the superconducting microwave resonator. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a block diagram illustrating a circuit including a Josephson ring modulator according to one embodiment of the present invention. [Figure 2] FIG. 1 is a block diagram illustrating a circuit including a superconducting surface acoustic wave resonator, according to one embodiment of the present invention. [Figure 3] FIG. 1 is a circuit diagram illustrating a circuit of a superconducting device including a surface acoustic wave resonator and a superconducting microwave resonator coupled to a Josephson ring modulator, according to one embodiment of the present invention. [Figure 4] 1 is a schematic diagram illustrating a system including a unitary Josephson mixer for surface acoustic waves (phonons) and microwave signals (photons), according to one embodiment of the present invention. [Figure 5] 1 is a schematic diagram illustrating a system including a lossless frequency converter between surface acoustic waves and microwave signals, according to one embodiment of the present invention. [Figure 6] 1 is a schematic diagram illustrating a system including a non-degenerate parametric Josephson amplifier for surface acoustic wave and microwave signals, according to one embodiment of the present invention. [Figure 7] 1 is a schematic diagram illustrating a system including an entangler of phonon and photon modes, according to one embodiment of the present invention. [Figure 8]1 is a flow diagram illustrating a method for mixing surface acoustic waves (phonons) and microwave signals (photons), according to one embodiment of the present invention. [Figure 9] 3 is a flow diagram illustrating a method for mixing a surface acoustic wave and a microwave signal based on the frequency of a microwave control signal, in accordance with one embodiment of the present invention. [Figure 10] 4 is a flow diagram illustrating a method of operating a switch used to mix surface acoustic waves and microwave signals based on the frequency and amplitude of a microwave control signal, in accordance with one embodiment of the present invention. [Figure 11] 3 is a flow chart illustrating a method for mixing a surface acoustic wave and a microwave signal based on the amplitude of the microwave signal, according to one embodiment of the present invention. [Figure 12] 1 is a flow chart illustrating a method for lossless frequency conversion between surface acoustic waves and microwave signals, according to one embodiment of the present invention. [Figure 13] 3 is a flow chart illustrating a method for upconverting a surface acoustic wave signal to a microwave signal in accordance with one embodiment of the present invention. [Figure 14] 3 is a flow chart illustrating a method for downconverting a microwave signal to a surface acoustic wave signal in accordance with an embodiment of the present invention. [Figure 15] 1 is a flow diagram illustrating a method for non-degenerate parametric amplification of surface acoustic wave and microwave signals according to one embodiment of the present invention. [Figure 16] 1 is a flow diagram illustrating a method for creating entanglement between phonon and photon modes in a quantum circuit, according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] The following detailed description is merely illustrative and is not intended to limit the embodiments of the invention or the application and / or uses of the invention, nor is it intended to be constrained by any express or implied information presented in the above "Background" or "Summary" sections or "Description of the Invention" sections.

[0017] DETAILED DESCRIPTION OF THE INVENTION

[0013] Embodiments of the present invention will now be described with reference to the drawings. Like reference numerals are used to refer to like elements throughout the drawings. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a better understanding of embodiments of the present invention. It will be apparent, however, that in various instances, embodiments of the present invention may be practiced without these details.

[0018] With respect to circuits, and more specifically, quantum circuits, when a Josephson ring modulator (JRM) is coupled to two superconducting wave resonators, there are limitations on the selection of differential modes. For example, a problem associated with coupling a JRM to a low-frequency transmission line resonator is the large area occupied by the device. As another example, a problem associated with coupling a JRM to a low-frequency lumped-element resonator is that the large capacitors are relatively lossy. The solution provided by the superconducting devices, superconducting circuits, and methods described herein is the use of superconducting surface acoustic wave resonators, which are compact and can therefore reduce the size and / or losses of the superconducting device.

[0019] Another problem with prior art superconducting devices (e.g., devices using two superconducting microwave resonators) is that they are limited to mixing frequencies between 5 gigahertz (GHz) and 15 GHz. The various superconducting devices, circuits, and methods described herein provide a solution to this problem through the use of a superconducting surface acoustic wave resonator and a superconducting microwave resonator, which enable dissipationless three-wave mixing and amplification between low microwave frequencies (e.g., from about 0.1 GHz to about 4 GHz) and high microwave frequencies (e.g., from about 5 GHz to about 15 GHz).

[0020] In view of the above-mentioned problems of prior art superconducting devices, various aspects presented herein can be implemented to provide solutions to one or more of the above-mentioned problems in the form of superconducting devices, superconducting circuits, and methods of fabricating the same. Such systems, devices, circuits, and methods can have the advantages of reduced size and low-loss resonators compared to prior art.

[0021] In some implementations, the device can function as one or more of: a Josephson mixer between surface acoustic waves (phonons) and microwave signals (photons); a lossless frequency converter between surface acoustic waves and microwave signals; a non-degenerate parametric Josephson amplifier for surface acoustic waves and microwave signals; and an entangler between phonon and photon modes.

[0022] Referring to FIG. 1, a circuit 100 includes a superconducting surface acoustic wave (SAW) resonator (referred to as superconducting SAW resonator 102), a superconducting microwave resonator 104, and a Josephson ring modulator (referred to as JRM 106).

[0023] In a piece of quantum hardware including a superconducting qubit space, a mechanism for performing gate operations or measurements on the quantum hardware generates or receives microwave signals by a superconducting SAW resonator 102, or through a superconducting microwave resonator 104, or both. The circuit 100 can operate as one or more of a Josephson mixer between surface acoustic waves (phonons) and microwave signals (photons), a lossless frequency converter between surface acoustic waves and microwave signals, a non-degenerate parametric Josephson amplifier for surface acoustic waves and microwave signals, and an entangler between phonon and photon modes.

[0024] SAW resonators (e.g., superconducting SAW resonators 102) are electromechanical resonators for phonons and can resonate at microwave frequencies from about 0.5 GHz to 5 GHz. SAW resonators (or SAW filters) are used in many telecommunications applications (e.g., cell phones). SAW resonators may also be useful in quantum computing applications and quantum circuits in the microwave region, as described herein. SAW resonators may also be useful in quantum circuits, as described herein. 5 SAW resonators can have high internal quality (Q) values ​​that can exceed 100 kHz. Therefore, SAW resonators can have extremely low losses. Furthermore, SAW resonators are very compact. For example, the surface acoustic wave resonant wavelength is very short (e.g., less than 1 micrometer, i.e., <1 μm).

[0025] The superconducting SAW resonator 102 can be a low frequency device, and the superconducting microwave resonator 104 can be a high frequency device. The superconducting SAW resonator 102 can be mounted on a low-loss piezoelectric dielectric substrate. The low-loss piezoelectric dielectric substrate can include a material selected from a group of materials including quartz, gallium arsenide, lithium niobate, or zinc oxide, or a combination thereof. The superconducting microwave resonator 104 can be implemented using lumped element capacitance and lumped element inductance. Further details regarding the superconducting SAW resonator 102 and the superconducting microwave resonator 104 are provided below with reference to FIGS. 2 and 3.

[0026] The JRM 106 may be a device based on a Josephson tunnel junction. For example, the JRM 106 may include one or more Josephson junctions arranged in a Wheatstone bridge configuration. The one or more Josephson junctions may include a material selected from a group of materials including aluminum and niobium. The JRM 106 may also perform non-degenerate mixing in the microwave band without loss. In some implementations, the JRM 106 may be a dispersive nonlinear three-wave mixing element.

[0027] The JRM 106 can support two differential modes and two common modes (one of which is at zero frequency and therefore not applicable to one or more embodiments described herein). By coupling the JRM 106 to a suitable electromagnetic environment (supporting two differential microwave modes), the circuit 100 can be used to perform various quantum processing operations, such as lossless frequency conversion in the microwave region, or parametric amplification at the quantum limit (e.g., amplification of quantum signals in the microwave region), or generating two-mode squeezing, or a combination thereof.

[0028] The JRM 106 may include one or more Josephson junctions arranged in a Wheatstone bridge configuration. The Josephson junctions are illustrated as first Josephson junction 108, second Josephson junction 110, third Josephson junction 112, and fourth Josephson junction 114. The Josephson junctions may be formed in a loop. The Josephson junctions may also be used to perform mixing as described herein.

[0029] The JRM 106 may also include four additional junctions (inside the loop), which may be shunt junctions in some implementations. These four additional junctions are labeled as a first internal junction 116, a second internal junction 118, a third internal junction 120, and a fourth internal junction 122. The four internal junctions may facilitate tuning of the frequency of the circuit 100. This tuning is achieved by applying an external magnetic flux. In this configuration, the four internal junctions are larger than the junctions on the external loop and may function as linear inductors shunting the external Josephson junctions. Passing an external magnetic flux through the internal loop may change the total inductance of the JRM 106, thereby causing a change in the resonant frequency of a resonator coupled to the JRM 106.

[0030] Additionally, the configuration of the JRM 106 defines the points or nodes where external junctions connect. Thus, there may be a first node 124 at the bottom of the JRM 106, a second node 126 at the right side of the JRM 106, a third node 128 at the top of the JRM 106, and a fourth node 130 at the left side of the JRM 106. It should be noted that the terms bottom, right, top, and left are intended to describe the disclosed embodiments with reference to the drawings and are not intended to limit the disclosed embodiments to any particular side or orientation of the JRM 106 and / or circuit 100 and associated circuitry.

[0031] The four nodes can be used to define the differential and common modes supported by circuit 100. The modes can be orthogonal and non-overlapping. Also, as shown, the nodes can be physically orthogonal. For example, first node 124 and third node 128 are perpendicular to each other, and second node 126 and fourth node 130 are horizontal to each other.

[0032] The nodes can be used to couple the JRM 106 to the superconducting SAW resonator 102 and the superconducting microwave resonator 104. For example, a first pair of opposing nodes (e.g., first node 124 and third node 128) can be selected to operably couple the JRM 106 to the superconducting SAW resonator 102. The first node 124 can be coupled to the superconducting SAW resonator 102 via a line 132 (or a first lead), and the third node 128 can be coupled to the superconducting SAW resonator 102 via a second line 134 (or a second lead).

[0033] A second pair of opposing nodes (e.g., second node 126 and fourth node 130) may be selected to operably couple JRM 106 to superconducting microwave resonator 104. For example, second node 126 may be coupled to superconducting microwave resonator 104 via third wire 136 (or third lead), and fourth node 130 may be coupled to superconducting microwave resonator 104 via fourth wire 138 (or fourth lead).

[0034] As shown, first wire 132 and second wire 134 may be coupled to superconducting SAW resonator 102 at different locations on superconducting SAW resonator 102. Additionally, third wire 136 and fourth wire 138 may be coupled to superconducting microwave resonator 104 at different locations on superconducting microwave resonator 104. Further details regarding coupling locations are provided below with reference to FIG. 3.

[0035] The superconducting SAW resonator 102, the superconducting microwave resonator 104, and the JRM 106 are part of a frequency converter / mixer / amplifier / entangler device that can receive external microwave photons or phonons from other quantum devices connected to the microwave and / or SAW ports of the device.

[0036] Circuit 100 and other aspects described herein can be utilized in devices that facilitate the manipulation of quantum information according to one or more embodiments described herein. Aspects of the devices (e.g., circuit 100), systems, apparatus, or processes described in this disclosure can constitute machine-executable components embodied in a machine, e.g., embodied in one or more computer-readable medium(s) associated with one or more machines. Such components, when executed by one or more machines, e.g., computers, computing devices, virtual machines, etc., can cause the machines to perform the described operations.

[0037] In various embodiments, a device may be any type of component, machine, system, device, mechanism, equipment, or combination thereof that includes a processor and / or may be capable of effective or operable communication with a wired and / or wireless network. Components, machines, equipment, systems, devices, mechanisms, or equipment that may include a device may include a tablet computing device, a handheld device, a server class computing machine or database, or combinations thereof, a laptop computer, a notebook computer, a desktop computer, a mobile phone, a smartphone, a consumer device or appliance, or combinations thereof, an industrial and / or commercial device, a handheld device, a digital assistant, a multimedia Internet enabled telephone, a multimedia player, etc.

[0038] In various embodiments of the present invention, the device may be a quantum computing device or system related to technologies such as, but not limited to, quantum circuit technology, quantum processor technology, quantum computing technology, artificial intelligence technology, pharmaceutical and materials technology, supply chain and logistics technology, financial services technology, or other digital technologies, or combinations thereof. Circuit 100 may utilize hardware and / or software to solve problems of a highly specialized nature that are not abstract and cannot be performed by humans as a set of mental activities. Additionally, in certain embodiments, portions of the processes performed may be performed by one or more specialized computers (e.g., one or more dedicated processing units, a dedicated computer with quantum computing components, etc.) for performing defined tasks related to machine learning.

[0039] The device and / or components of the device can be employed to solve new problems arising from advances in the above technologies and / or computer architectures, etc. One or more embodiments of the device may provide technical improvements to quantum computing systems, quantum circuit systems, quantum processor systems, artificial intelligence systems, or other systems, or combinations thereof, and may also provide technical improvements to quantum processors (e.g., superconducting quantum processors) by improving the processing performance of the quantum processor, the processing efficiency of the quantum processor, the processing characteristics of the quantum processor, the timing characteristics of the quantum processor, or by improving the power efficiency of the quantum processor, or combinations thereof.

[0040] 2, a circuit 200 includes a superconducting SAW resonator 102 that may include a first superconducting metal / dielectric mirror (e.g., Bragg mirror 202) and a second superconducting metal / dielectric mirror (e.g., second Bragg mirror 204). The first Bragg mirror 202 may be separated from the second Bragg mirror 204 by a distance that is an odd integer multiple of the half wavelength supported by the superconducting SAW resonator 102. The Bragg mirrors include a periodic structure of metal fingers and dielectric gaps positioned at a specified distance from each other.

[0041] According to some implementations, the superconducting SAW resonator 102 can be attached (e.g., mounted) to a low-loss piezoelectric dielectric substrate (not shown), which can include a material selected from a group of materials including one or more of quartz, gallium arsenide, lithium niobate, and zinc oxide or similar materials.

[0042] Also included may be a first interdigital capacitance device or first IDC device 206 and a second IDC device 208. The first IDC device 206 may be coupled between the superconducting SAW resonator 102 and the JRM 106. The second IDC device 208 may be coupled between the superconducting SAW resonator 102 and an external port (e.g., signal port 212).

[0043] For example, the first IDC device 206 may be located at the center of the superconducting SAW resonator 102. A first set of opposing nodes of the JRM 106 may be connected to opposing nodes of the first IDC device 206. For example, the first node 124 of the JRM 106 may be connected to a first side of the first IDC device 206 (e.g., via a first line 132). Additionally, the third node 128 of the JRM 106 may be connected to a second side of the first IDC device 206 (e.g., via a second line 134).

[0044] A second set of opposing nodes of the Josephson ring modulator can be connected to the superconducting microwave resonator 104. For example, the second node 126 of the JRM 106 can be connected (e.g., via a third line 136) to a first side of the superconducting microwave resonator 104, and the fourth node 130 of the JRM 106 can be connected (e.g., via a fourth line 138) to a second side of the superconducting microwave resonator.

[0045] The circuit 100 may also include a first external feed line 210 coupled to the superconducting SAW resonator 102 via the second IDC device 208. The first external feed line 210 may be connected to a signal port 212 (e.g., a radio frequency (rf) source). The first external feed line 210 may carry one or more input signals and one or more output signals for the superconducting SAW resonator 102.

[0046] A second external feed line 214 may be coupled to the superconducting microwave resonator 104. The second external feed line 214 may be connected to an idler port 216 (e.g., a microwave source). The second external feed line 214 may carry one or more input signals and one or more output signals for the superconducting microwave resonator 104.

[0047] Additionally, the JRM 106 can be operably connected to a pump port 218 (e.g., by the second line 134 or other wiring). The pump port 218 can be connected to a microwave source. The pump port 218 can provide the necessary energy for operation of the circuit 100. For example, the superconducting SAW resonator 102 and the superconducting microwave resonator 104 can be electrically connected via the JRM 106 at or after pump power is supplied from the pump port 218 to the JRM 106. However, when power is not supplied via the pump port 218 (e.g., the power supply is off), the superconducting SAW resonator 102 and the superconducting microwave resonator 104 can be electrically isolated from each other.

[0048] Ideally, for amplification, there would be a microwave signal propagating on an idler transmission line (e.g., second external feed line 214) connected to idler port 216. In one embodiment, the microwave signal is weak and carries some useful quantum information. This information is a pump tone that enters circuit 100 and is fed (e.g., via pump port 218) to a device that can create parametric amplification between the idler mode and the signal mode supported by superconducting SAW resonator 102. In this example, no input signal is required at both signal port 212 and idler port 216. Instead, a signal is required only on one port, and quantum noise can enter via the other port. The deterministic signal carrying the quantum information and the quantum noise can be mixed by the device via the pump drive and amplified upon exiting the device. Thus, the information-carrying signal can come from either signal port 212 or idler port 216, or there can be two information-carrying signals entering both ports substantially simultaneously. For simplicity, assume that a signal enters the circuit 100 through one port, while the other port receives only quantum noise. In this case, the interaction of the pump (e.g., pump port 218) with the JRM 106 results in three-wave mixing between the common mode (pump) and two differential modes (idler and signal). When the pump frequency is the sum of the signal and idler resonant frequencies, the device functions as a phase-preserving parametric amplifier operating near the quantum limit. The respective output signals exiting the signal port 212 and the idler port 216 can be an amplified superposition of the input signals entering both ports (e.g., signal port 212 and idler port 216).

[0049] According to some implementations, magnetic flux through the JRM 106 can be induced via one or more external superconducting magnetic coils, for example, using external superconducting magnetic coils attached to the device package or using on-chip magnetic flux lines.

[0050] Referring to FIG. 3, a circuit 300 includes a surface acoustic wave resonator and a superconducting microwave resonator coupled to a Josephson ring modulator.

[0051] Note that in Figure 3, for simplicity, the Josephson junctions and four internal junctions of the JRM 106 are not numbered, but for illustrative purposes the numbering of the junction elements is the same as the labeling in Figures 1 and 2. Also, circuit 300 and its associated components may be implemented on a single chip in some implementations.

[0052] As described above, the nodes of the JRM 106 may include a first set of opposing nodes that may be oriented perpendicular to one another. For example, the first set of opposing nodes may include the first node 124 and the third node 128 that may operably couple the JRM 106 to the superconducting SAW resonator 102 (e.g., via the first line 132 and the second line 134). Additionally, the nodes of the JRM 106 may include a second set of opposing nodes that may be oriented horizontally. For example, the second set of opposing nodes may include the second node 126 and the fourth node 130 that may operably couple the JRM 106 to the superconducting microwave resonator 104. While illustrated and described with respect to a horizontal and / or vertical orientation, it should be noted that aspects of the present disclosure are not limited to this orientation and other orientations may be used.

[0053] A first set of opposing nodes (e.g., first node 124 and third node 128) may be coupled to opposing electrodes of a first interdigital capacitor or first IDC 302 (e.g., first IDC device 206) of the superconducting SAW resonator 102, thereby forming a first orthogonal mode. For example, the first node 124 of the JRM 106 may be coupled to a first electrode of the first IDC 302, shown at 304. Additionally, the third node 128 of the JRM 106 may be coupled to a second electrode of the first IDC 302, shown at 306. The first IDC 302 may be located at the center of the superconducting SAW resonator 102.

[0054] A second set of opposing nodes (e.g., second node 126 and fourth node 130) can be coupled to a second capacitor 310 (e.g., a shunt capacitor) to form a superconducting microwave resonator 104, where the JRM is the inductive element of the resonator. The superconducting microwave resonator can support a second orthogonal differential mode of the JRM 106. A capacitance (e.g., first capacitor 308) serves as a coupling capacitor between the microwave resonator (formed by the JRM 106 and second capacitor 310) and the device's external supply line / port (e.g., idler port 216). In some implementations, the first capacitor 308 and the second capacitor 310 can each be selected from a group of capacitors including a gap capacitor, an interdigitated capacitor, a plate capacitor, or a combination thereof. For a plate capacitance, the dielectric material must have extremely low loss, at the level of a single microwave photon.

[0055] As shown, the superconducting SAW resonator 102 may include a first IDC 302, a second IDC 312 (e.g., second IDC device 208), and a pair of metal / dielectric mirrors (e.g., first Bragg mirror 202 and second Bragg mirror 204). The components of the superconducting SAW resonator 102 (e.g., first IDC 302, second IDC 312, first Bragg mirror 202, second Bragg mirror 204) are mounted on a piezoelectric substrate. For example, the piezoelectric substrate may include one or more of quartz, gallium arsenide, lithium niobate, zinc oxide, or similar materials or combinations thereof.

[0056] Different ports can be used to access the superconducting SAW resonator 102 and the superconducting microwave resonator 104. For example, a signal port 212 can be used to access the superconducting SAW resonator 102, and an idler port 216 can be used to access the superconducting microwave resonator 104.

[0057] The signal port 212 can be used to carry input and output signals. Therefore, to measure the output signal from the superconducting SAW resonator 102, an IDC (e.g., the second IDC device 208) can be placed between the first Bragg mirror 202 and the second Bragg mirror 204. A pair of interconnected IDC fingers are positioned at the RF voltage antinodes (maximum / minimum) of the supported phonon mode. Therefore, the spacing between the fingers can depend on the wavelength supported by the superconducting SAW resonator 102.

[0058] The distance between the centers of two consecutive fingers of an IDC (e.g., the first IDC 302 and the second IDC 312) is λ a / 2. According to one implementation, each pair of fingers of the IDC can have opposite polarities. Also, as shown by line 314, the first Bragg mirror 202 and the second Bragg mirror 204 can be separated from each other by a distance of an odd integer multiple of the half wavelength supported by the superconducting SAW resonator 102. The specified distance is L a where L a is λ a / 2, where λ is an odd integer multiple. b <λ a is.

[0059] A microwave tone is characterized by a wave having a maximum and a minimum amplitude. The minimum amplitude must couple to one finger (e.g., designated 304 or 306) of the IDC, and the maximum must couple to the other finger (e.g., designated 304 or 306), which are connected to opposite nodes (e.g., first node 124 and third node 128) of the JRM 106. Thus, the distance λ a / 2 can be chosen to encourage a maximum in the first finger and a minimum in the other finger.

[0060] Also, for purposes of illustration, maximum amplitude has a plus sign (or positive value) and minimum amplitude has a minus sign (or negative value). Thus, two opposite nodes of the JRM106 can be excited by a positive rf voltage (on the first finger) and a negative rf voltage (on the second finger). These signals may alternate in time; however, they must always be opposites. When the polarities are opposite, this is sometimes called differential mode (differential here means opposite sign).

[0061] This may also be the case for the superconducting microwave resonator 104. As previously mentioned, the superconducting microwave resonator may include a first capacitor 308 that couples the resonator to an external port (e.g., idler port 216) and a second capacitor 310 that shunts the JRM 106. The two electrodes of the capacitor (e.g., second capacitor 310) that shunts the JRM 106 may have opposite voltages, exciting a second differential mode. Thus, the first differential mode of the JRM 106 is supported by the superconducting SAW resonator 102, and the second differential mode of the JRM 106 is supported by the superconducting microwave resonator 104.

[0062] Microwave energy for device operation is also provided to perform mixing or amplification. The energy source for mixing and / or amplification is provided via pump port 218. Pump port 218 can provide a microwave signal, which can be a strong, coherent, non-resonant microwave tone, that can provide the energy for circuit 100 to operate. In some implementations, the microwave signal provided by pump port 218 can include frequencies that satisfy a predefined equation determined based on the energy conservation of three-wave mixing performed in circuit 100.

[0063] In one embodiment of the amplification performed by the device, the first signal f a is within the bandwidth of the superconducting SAW resonator 102, and the second signal f b is within the bandwidth of the superconducting microwave resonator 104. Also, the frequency of the second signal may be greater than the frequency of the first signal (f b >f a To amplify both signals, the frequency of the pump tone supplied through pump port 218 is set to the sum of the first and second signals (e.g., f a +f b) The energy of an electromagnetic signal is proportional to its frequency. By summing the pump (e.g., pump port 218) frequency, when the pump interacts with a dispersive nonlinear medium (e.g., JRM106), the energy photons of the pump are a The first pair of photons in and f b A down-conversion process can occur in which photons split into a second set of photons at a lower frequency f a the first half (e.g., the first set of photons) at b The pump can then be split into two halves (e.g., a second set of photons) at f. Thus, the pump exchanges energy with the signal and idler modes, and this exchange generates entangled photons in both modes, so amplification can occur. Similarly, conversion processes with non-phonon-to-photon gain can convert one mode to the other (e.g., photon to phonon or phonon to photon). In this case, the pump frequency is f a and f b must be equal to the difference between f b is larger, so the formula is f b -f a It could be.

[0064] According to one implementation, the mixing process (photon-phonon gainless conversion) can upconvert phonons in the SAW resonator at the signal frequency to microwave photons in the microwave resonator at the idler frequency. According to another implementation, photons in the microwave resonator at the idler frequency can downconvert photons in the SAW resonator at the signal frequency. This energy exchange can be enabled by a pump drive (e.g., provided via pump port 218). Thus, pump photons are emitted or pump photons are absorbed to facilitate this process.

[0065] When no pump signal is applied to pump port 218, superconducting SAW resonator 102 and superconducting microwave resonator 104 are decoupled (isolated from each other), and no information exchange or transmission occurs between superconducting SAW resonator 102 and superconducting microwave resonator 104. Simultaneously with or after a pump signal is applied to pump port 218, the pump signal excites the common mode of JRM 106 as shown in Figure 2, causing superconducting SAW resonator 102 and superconducting microwave resonator 104 to interact and exchange information.

[0066] In some implementations, the pump drive is supplied through a sigma port of a 180-degree hybrid 316 that is capacitively coupled to opposite nodes of the JRM 106, which excites the common mode of the JRM 106. In some implementations, the 180-degree hybrid 316 acts as a power splitter.

[0067] For purposes of explanation, but not limitation, a 180-degree hybrid is a passive microwave component that includes four ports. The first port is referred to as the sum port 318 (or sigma port). When a signal is input to the sum port 318, the signal is split equally to two other ports (e.g., a second port 320 and a third port 322). The signals output from the second port 320 and the third port 322 may have the same phase. Therefore, the first port is referred to as the sum port 318 because the split signals are equal in phase. A pump drive (e.g., pump port 218) can be supplied through the sum port 318 of the 180-degree hybrid 316.

[0068] The fourth port can be called the delta port 324 (or differential port). When a signal is injected through the delta port 324 of the 180-degree hybrid (terminated at 50 ohms in Figure 3), the hybrid splits the signal into two signals that exit two ports (e.g., the second port 320 and the third port 322), with the split signals having a 180-degree phase difference. For example, when the first signal has a maximum value at one port (e.g., 320), the second signal at the other port (e.g., 322) has a minimum value. The pump port 218 can be fed through the sum port 318.

[0069] Also shown are a first lead 326 from the second port 320 and a second lead 328 from the third port 322. The signals output at the second and third ports are half the pump signal and have the same phase, as described above. These signals lead to small coupling capacitors (e.g., first coupling capacitor 330 and second coupling capacitor 332) that can be coupled to two opposite nodes of the JRM 106. In some implementations, the first and second coupling capacitors 330 and 332 can be respective capacitors selected from a group of capacitors including gap capacitors, interdigitated capacitors, and plate capacitors. For plate capacitors, the dielectric material must have extremely low loss, at the level of a single microwave photon.

[0070] A first coupling capacitor 330 can be coupled to the first node 124 of the JRM 106 (via the first IDC 302), and a second coupling capacitor 332 can be coupled to the third node 128 of the JRM 106. More specifically, the first lead 326 and the second lead 328 can be coupled to two different sets of fingers (shown at the first contact 306 and the third contact 334) of the first IDC 302 that couple to two opposite nodes of the JRM 106. This connection allows for excitation of a common mode of the JRM 106, in which the two opposite nodes are excited with equal but not different rf signs of the JRM 106. For example, the two opposite nodes can be excited with a positive-positive signal or a negative-negative signal.

[0071] The first lead wire 326 and the second lead wire 328 may be connecting superconducting wires that must be equal in length (e.g., phase-matched) between the ports of the 180-degree hybrid (e.g., second port 320, third port 322) and the coupling capacitors (e.g., first coupling capacitor 330, second coupling capacitor 332, respectively). Similarly, the first wire 132 and the second wire 134 may be connecting superconducting wires that must be equal in length (e.g., phase-matched) between opposite nodes of the JRM 106 and the electrodes of the first IDC 302. The third wire 136 and the fourth wire 138 may be connecting superconducting wires that must be equal in length (e.g., phase-matched) between opposite nodes of the JRM 106 and the electrodes of the second capacitor 310. The connecting superconducting wires should also be as short and wide as possible (e.g., have low series inductance).

[0072] The following provides further technical explanation to facilitate understanding of various aspects disclosed herein. The speed of sound in various piezoelectric substrates is several orders of magnitude (e.g., about 5 orders of magnitude, e.g., 10 orders of magnitude) faster than the speed of light. 5 ) may be slow.

[0073] The effective length of the superconducting SAW resonator 102 is L aThis may be because the reflection of the Bragg mirror does not occur at the edge of the mirror but within a certain penetration depth inside the Bragg mirror.

[0074] The effective length (L eff ) and the velocity of sound in the piezoelectric substrate (v s ) may determine the cavity free spectral range (FSR) as follows:

number

[0075] The larger the spacing between the Bragg mirrors, the eff The Bragg mirror can act as a reflector within a certain bandwidth. Modes outside the bandwidth of the Bragg mirror are not supported by the SAW resonator because the phonon modes are not confined.

[0076] V FSR Depending on the bandwidth of the Bragg mirror and the SAW resonator, the circuit 100 can operate over a single mode, a few modes, or multiple modes of the SAW resonator. Note that not all modes supported by the SAW resonator will be strongly coupled to the JRM. Three-wave mixing operation in the circuit 100 can occur due to phonon modes that strongly couple to the JRM. A mode strongly couples to the JRM when its antinode coincides with an IDC finger that is coupled to the JRM.

[0077] The circuit 100 can be a three-wave mixer, such as a Josephson mixer, which relies on the nonlinear inductance of a lossless Josephson junction. A Josephson mixer can be used to enable mixing of microwave signals carried by photons with phonons supported by a superconducting SAW resonator 102. This differs from conventional devices that couple phonons to phonons or photons to photons. Therefore, embodiments of the present disclosure provide significant improvements in coupling. For example, the circuit 100 can enable conversion of microwave signals to acoustic waves resonating at low microwave frequencies. The circuit 100 can also provide nondegenerate amplification. Nondegenerate here means that (1) circuit 100 amplifies two different frequencies, one at a high microwave frequency (e.g., 12 GHz) and another at a relatively low microwave frequency (e.g., 1 GHz), and therefore nondegenerate because the frequencies are different and therefore spectrally nondegenerate; and (2) the microwave signal is supported by superconducting microwave resonator 104, which is physically different from superconducting SAW resonator 102, which supports the surface acoustic wave, and therefore spatially nondegenerate. Thus, there is spectral nondegenerate and physical nondegenerate. This process of nondegenerate parametric amplification allows circuit 100 to entangle phonon modes with photon modes, where entanglement is a quantum property in which the two modes are highly correlated and inseparable from each other. Therefore, measuring one allows the state of the other to be determined. Thus, the two are entangled and form a single entity, but they can be separated by distance in space.

[0078] 4, system 400 includes a unitary Josephson mixer for surface acoustic waves (phonons) and microwave signals (photons). System 400 may include one or more of the components and / or functions of circuit 100, or vice versa.

[0079] System 400 may include a microwave Josephson mixer 402 (e.g., circuit 100 of FIG. 1). Mixers conventionally used in communications or other microwave applications are capable of mixing microwave signals. However, conventional mixers do not losslessly mix SAW waves and microwave signals as described herein and facilitated by microwave Josephson mixer 402.

[0080] The microwave Josephson mixer 402 can receive a surface acoustic wave signal (e.g., SAW signal 404) from the superconducting SAW resonator 102 (of the circuit 100). The SAW signal 404 can include one or more phonons capable of resonating at a first frequency. The microwave Josephson mixer 402 can also receive a microwave signal 406 from the superconducting microwave resonator 104 (of the circuit 100). The microwave signal 406 can include one or more photons capable of resonating at a second frequency. For example, there can be a first port (e.g., signal port 212) capable of supporting the SAW signal 404 and a second port (e.g., idler port 216) capable of supporting the microwave signal 406. A third port (e.g., pump port 218) can support a microwave control signal 408 (also referred to as a microwave drive signal).

[0081] The microwave control signal 408 may have a second frequency (f2) greater than the first frequency f1 of the SAW signal 404, and a third frequency (f d ) in one embodiment, the microwave control signal 408 may have a frequency (f d ) can be set equal to the absolute value of the difference between the frequency of the microwave signal 406 (f2) and the frequency of the SAW signal 404 (f1). d =|f2-f1|.

[0082] The microwave Josephson mixer 402 can operate as a lossless microwave Josephson mixer between the photon-supported SAW signal 404 and the photon-carried microwave control signal 408. For purposes of explanation, and not limitation, in standard microwave Josephson mixer terminology, the frequency (f1) of the SAW signal 404 corresponds to an intermediate frequency (IF), the microwave signal frequency (f2) corresponds to a radio frequency (RF), and the frequency f of the microwave control signal 408 (or drive signal) corresponds to a frequency (f3) of the SAW signal 404. d =|f1-f2| may correspond to a local oscillator (LO).

[0083] Quantum information carried and / or stored by superconducting SAW resonator 102 can be transferred to or from superconducting microwave resonator 104 using microwave Josephson mixer 402 and microwave control signal 408. Thus, microwave Josephson mixer 402 can mix SAW signal 404 and microwave signal 406 based on microwave control signal 408 received from a microwave source (e.g., provided via pump port 218).

[0084] Microwave Josephson mixer 402 can transfer information from superconducting SAW resonator 102 to superconducting microwave resonator 104 based on a first frequency of microwave control signal 408. In another embodiment, microwave Josephson mixer 402 can transfer information from superconducting microwave resonator 104 to superconducting SAW resonator 102 based on a second frequency of microwave control signal 408. For example, a microwave source (e.g., at pump port 218) can be operated at a first frequency for a first transfer of first information from superconducting SAW resonator 102 to superconducting microwave resonator 104. Also, the microwave source can be operated at a second frequency for a second transfer of second information from superconducting microwave resonator 104 to superconducting SAW resonator 102.

[0085] 4, the signal is input at the superconducting SAW resonator 102 and output at the superconducting microwave resonator 104. However, the device can also be bidirectional, with the signal input at the superconducting microwave resonator 104 and output at the superconducting SAW resonator 102. The pump frequency is the same in both cases.

[0086] According to some implementations, the microwave Josephson mixer 402 can be used as a switch to connect and / or disconnect the superconducting SAW resonator 102 to and from the superconducting microwave resonator 104. The connection and / or disconnection can be based on the presence or absence of a microwave control signal 408. For example, in the absence of the microwave control signal 408, the superconducting SAW resonator 102 and the superconducting microwave resonator 104 are not connected (e.g., no information is transferred between the resonators). However, in the presence of the microwave control signal 408, the microwave Josephson mixer 402 can facilitate the transfer of information between the superconducting SAW resonator 102 and the superconducting microwave resonator 104.

[0087] Additionally, the amplitude of microwave control signal 408 can be varied by the microwave source generating microwave control signal 408. The amplitude of microwave control signal 408 can determine whether all or part of the quantum information is transferred (converted) between two resonators / modes. Thus, the frequency of microwave control signal 408 can be used by microwave Josephson mixer 402 to select the mode in which information is exchanged or converted. Additionally, microwave Josephson mixer 402 can preserve the energy and coherence of the quantum signal (information) being transferred.

[0088] 5, system 500 includes a lossless frequency converter between surface acoustic waves and microwave signals. System 500 may include one or more of the components or functions of circuit 100, system 400, or a combination thereof, or vice versa.

[0089] As shown, system 500 may include superconducting SAW resonator 102, superconducting microwave resonator 104, and JRM 106. In this mode of operation, the amplitude of microwave control signal 408 (at pump port 218) may enable full transfer of quantum information between superconducting SAW resonator 102 and superconducting microwave resonator 104. In addition to this mode of operation, the microwave frequency of the signal carrier may be upconverted or downconverted (depending on whether the device's input signal is SAW signal 404 or microwave reflected signal 508, respectively).

[0090] More specifically, a propagating radio frequency (RF) signal in the range of approximately 0.5 GHz to approximately 5 GHz can be mapped to a phonon mode in the superconducting SAW resonator 102. Application of a microwave control signal 408 can upconvert the phonon mode into the superconducting microwave resonator 104, thereby creating a lossless three-wave mixing interaction. The upconverted microwave signal is then ready to propagate once it exits the superconducting microwave resonator. A frequency converter 502 (e.g., circuit 100 of FIG. 1) in system 500 can also perform the reverse process, as shown by SAW reflected signal 506. Thus, the frequency of the signal can be converted from f1 to f2 or from f2 to f1.

[0091] A pump signal (e.g., microwave control signal 408) can be used to facilitate the conversion. For example, a SAW signal 404 can propagate through a transmission line 504 that can be associated with a phonon mode in the superconducting SAW resonator 102. Thus, the frequency converter can receive the SAW signal 404 from the superconducting SAW resonator 102, which can include one or more phonons that resonate at a first frequency.

[0092] The SAW signal 404 may be three-wave mixed in the JRM 106. To facilitate this three-wave mixing, the frequency converter 502 may receive a microwave control signal 408.

[0093] At or after the three-wave mixing, the JRM 106 can upconvert the SAW signal 404 to a microwave signal 406. The upconverted signal can exit the idler port 216 and propagate down the transmission line 504. For example, the frequency converter 502 can perform a lossless frequency conversion between a first input of the superconducting SAW resonator 102 and a second input of the superconducting microwave resonator 104 based on a pump signal (e.g., microwave control signal 408) received from a microwave source. The reverse process works similarly.

[0094] Microwave control signal 408 frequency (f d ) can be set equal to the absolute value of the difference between the frequency of the microwave signal 406 (f2) and the frequency of the SAW signal 404 (f1). d =|f2−f1|. Therefore, the first value of the microwave control signal frequency can be set to a value equal to the absolute value of the frequency difference between the resonant frequencies of the superconducting microwave resonator 104 and the superconducting SAW resonator 102.

[0095] According to some embodiments, performing lossless frequency conversion may include mapping a propagating radio frequency signal to a phonon mode in the superconducting SAW resonator 102. In addition to these embodiments, the frequency converter 502 may upconvert a phonon mode to a photon mode in the superconducting microwave resonator 104 upon application of a microwave control signal frequency (e.g., microwave control signal 408) of a defined frequency. The upconversion of the phonon mode is facilitated by lossless three-wave mixing interactions, and the upconverted microwave signal may propagate upon exiting the superconducting microwave resonator 104.

[0096] According to one embodiment, implementation of lossless frequency conversion may include mapping a propagating radio frequency signal to a photon mode in the superconducting microwave resonator 104. In addition to these embodiments, the frequency converter 502 may downconvert the photon mode to a phonon mode in the superconducting SAW resonator 102 by application of a microwave control signal 408 of a defined frequency. The downconversion of the photon signal may be facilitated by lossless three-wave mixing interactions. Additionally, the downloaded surface acoustic wave signal may propagate upon exiting the superconducting SAW resonator 102.

[0097] According to some implementations, the frequency converter 502 can transfer information from the superconducting SAW resonator 102 to the superconducting microwave resonator 104 based on the frequency of the microwave control signal 408. Additionally or alternatively, the frequency converter 502 can transfer information (e.g., quantum information) from the superconducting microwave resonator to the superconducting surface acoustic wave resonator based on the frequency of the microwave control signal.

[0098] The conversion process in system 500 (and other systems described herein) can be partial. Thus, a first set of information can be converted, while a second set of information can be retained and reflected back to the respective input ports. Also, a portion of the information can be converted using a switch (e.g., implemented by JRM 106 and the presence or absence of microwave control signal 408), where frequency determines which SAW modes are coupled to the microwave signal as a selector and / or switch. In the case of a switch, no conversion occurs in the absence of a pump signal.

[0099] 6, system 600 includes a non-degenerate parametric Josephson amplifier for surface acoustic wave and microwave signals. System 600 may include one or more of the components and / or functionality of circuit 100, system 400, system 500, or vice versa.

[0100] System 600 may include a Josephson parametric amplifier 602 that can function as a phase-preserving quantum-limited amplifier for low-frequency and high-frequency microwave signals. Two orthogonal components of an incident microwave signal entering two ports (e.g., signal port 212 and idler port 216) can be amplified at the quantum limit. The amplified output signal may include an amplified SAW signal 605 and an amplified microwave signal 606. The amplified output signal may include a same-frequency signal reflected at the same port and a frequency-converted signal transmitted to the other port. The incident signal is represented as a small arrow (e.g., a weak signal), and the output signal is represented as a larger arrow to indicate amplification. Microwave signals and other parametric signals may be defined by two orthogonal components: signal amplitude and signal phase.

[0101] More specifically, the propagating radio frequency signal and microwave signal can be mapped to at least one of the phonon modes of the superconducting SAW resonator 102 and at least one of the microwave modes of the superconducting microwave resonator 104, respectively. According to some implementations, the phonon and microwave modes can be fundamental modes, although the disclosed aspects are not limited to fundamental modes and other modes can be used. The phonon and microwave modes can be amplified at the quantum limit by application of a microwave drive signal that creates a lossless three-wave mixing interaction and can be mapped back to reflected (e.g., same frequency) and transmitted (e.g., different frequency) amplified radio frequency / microwave signals.

[0102] The amplification of system 600 is non-degenerate. Therefore, two modes can have two different frequencies and two different ports. The amplification produced by system 600 can preserve the phase of the microwave signal. Therefore, system 600 can amplify both orthogonal components of the microwave field by the same or similar amounts. For example, if one orthogonal component is amplified by 100 times, the other orthogonal component is also amplified by 100 times.

[0103] In some implementations, the Josephson parametric amplifier 602 can amplify a first quadrature component of the SAW signal 404 input to a first port (e.g., the signal port 212) and a second quadrature component of the microwave signal 406 input to a second port (e.g., the idler port 216). The first quadrature component can have a first amplitude and a first phase, and the second quadrature component can have a second amplitude and a second phase. A first amplified signal can be output from an output port. The first amplified signal can include a first reflected signal and a first transmitted signal, and the second amplified signal can include a second reflected signal and a second transmitted signal. The amplification can include amplifying the first quadrature component of the surface acoustic wave signal and the second quadrature component of the microwave signal by a defined amplification gain.

[0104] For example, the first reflected signal can include a first same-frequency signal reflected at the first port, the first transmitted signal can include a first frequency-converted signal transmitted to the second port, and the second reflected signal can include a second same-frequency signal reflected at the second port, and the second transmitted signal can include a second frequency-converted signal transmitted to the first port.

[0105] 7, system 700 includes a phonon mode entangler. System 700 may include one or more of the components and / or functionality of circuit 100, system 400, system 500, system 600, or vice versa.

[0106] System 700 may include an entanglement component 702 capable of entangling a phonon mode and a photon mode. System 700 may also include a first superconducting qubit 704 capacitively coupled to superconducting SAW resonator 102 and a second superconducting qubit 706 capacitively coupled to superconducting microwave resonator 104. JRM 106 may also be coupled to superconducting SAW resonator 102 and superconducting microwave resonator 104. System 700 may also include a pump drive (e.g., provided via pump port 218) operably coupled to two adjacent nodes of JRM 106 via first coupling capacitor 330 and second coupling capacitor 332.

[0107] According to one implementation, pump port 218 can input an input signal including a first frequency to JRM 106. A first superconducting qubit 704 can be operably coupled to entanglement component 702 via superconducting SAW resonator 102, and a second superconducting qubit 706 can be operably coupled to entanglement component 702 via superconducting microwave resonator 104. Additionally, entanglement component 702 can output an output signal including an entangled signal including the second frequency of superconducting SAW resonator 102 and the third frequency of superconducting microwave resonator 104. According to some implementations, entanglement component 702 can generate an entangled signal between one or more phonons of a surface acoustic wave output by superconducting SAW resonator 102 (e.g., amplified SAW signal 604) and one or more microwave photons output by superconducting microwave resonator 104 (e.g., amplified microwave signal 606).

[0108] When entanglement component 702 is operated as a non-degenerate amplifier, entanglement can be created between the phonons of the SAW signal supported by superconducting SAW resonator 102 and the microwave photons supported by superconducting microwave resonator 104. For example, this entanglement can be used to create an entangled state of a superconducting qubit capacitively coupled to entanglement component 702. Note that in practice, the qubit is not directly connected to entanglement component 702. Instead, the qubit is coupled to a microwave readout resonator, which is coupled to entanglement component 702.

[0109] In some implementations, parametric amplification can produce entanglement. Entanglement can occur when the reflected signal is not simply an amplified version of the incident signal but is an entanglement of the input signal. For example, the entangled signal can contain some information coming from the other port. Note that the signal is not simply reflected with gain or amplified and reflected. Because three-wave mixing occurs, part of the signal is reflected and another part is frequency-converted and transmitted to the other port. For example, the output microwave signal is not simply the amplified input microwave signal but also contains a portion of the SAW signal that has been amplified and frequency-upconverted. Thus, the output microwave signal can be a mixture of the reflected incident microwave signal via the idler port 216 and the frequency-converted transmitted SAW signal coming through the signal port 212. Thus, the output microwave signal can carry information containing parts of the two input signals.

[0110] As shown, there may be one or more qubits, shown as first superconducting qubit 704 and second superconducting qubit 706, coupled to entanglement component 702. Note that for simplicity, protection elements (e.g., components that protect the qubits from the amplified signal) between first superconducting qubit 704 and entanglement component 702 and between second superconducting qubit 706 and entanglement component 702 are not shown (such as microwave circulators and isolators). d is the sum of the two frequencies. Thus, the information of the first superconducting qubit 704 can be entangled with the information of the second superconducting qubit 706. Thus, the first superconducting qubit 704 and the second superconducting qubit 706 are effectively entangled.

[0111] For example, a first measurement can be made on a first superconducting qubit 704, and a second measurement can be made on a second superconducting qubit 706. The first and second measurements enter entanglement component 702 and are amplified at the output. Thus, a joint measurement of the first and second measurements can be made. The joint measurement creates entanglement between first superconducting qubit 704 and second superconducting qubit 706. In this configuration, first superconducting qubit 704 can be strongly coupled to multiple modes, while second superconducting qubit 706 can be coupled to a single mode.

[0112] FIG. 8 is a flow diagram illustrating an exemplary non-limiting method 800 for mixing surface acoustic waves (phonons) and microwave signals (photons).

[0113] At 802 of method 800, a surface acoustic wave signal (e.g., SAW signal 404) including one or more phonons capable of resonating at a low frequency can be received (e.g., by microwave Josephson mixer 402). The surface acoustic wave signal can be received from a superconducting surface acoustic wave resonator (e.g., superconducting SAW resonator 102) of a device (e.g., circuit 100). For example, an external signal coming from a quantum system can enter a device port and be mapped to phonon and photon modes in the microwave and SAW resonators.

[0114] Also, at 804 of method 800, a microwave signal (e.g., microwave signal 406) including one or more photons capable of resonating at a second frequency can be received (e.g., by microwave Josephson mixer 402). The microwave signal can be received from a superconducting microwave resonator (e.g., superconducting microwave resonator 104).

[0115] At 806 of method 800, a surface acoustic wave signal and a microwave signal can be mixed (e.g., by microwave Josephson mixer 402). The mixing can be based on a microwave control signal (e.g., microwave control signal 408) received from a microwave source (e.g., provided from pump port 218). According to some implementations, mixing the surface acoustic wave signal and the microwave signal can include preserving quantum information carried by the surface acoustic wave signal, the microwave signal, or both, via the microwave Josephson mixer and the microwave control signal. Thus, an external signal coming from the quantum system enters the device port and is mapped to phonon and photon modes in the microwave and SAW resonators.

[0116] The method 800 can perform dissipationless three-wave mixing and amplification between a low microwave frequency of a superconducting surface acoustic wave resonator and a high microwave frequency of a superconducting microwave resonator. It can also unitarily convert quantum information carried by a surface acoustic wave signal to a microwave signal or vice versa (e.g., preserving the energy and phase coherence of the quantum signal). This quantum operation can also be controlled and enabled by a separate microwave control signal (called a pump) received by the device.

[0117] FIG. 9 is a flow diagram illustrating a method 900 for mixing a surface acoustic wave and a microwave signal based on the frequency of a microwave control signal.

[0118] At 902 of method 900, a surface acoustic wave signal (e.g., SAW signal 404) and a microwave signal (e.g., microwave signal 406) can be mixed (e.g., by microwave Josephson mixer 402). For example, mixing by the microwave Josephson mixer can be based on a microwave control signal (e.g., microwave control signal 408) received from a microwave source operably coupled to the microwave Josephson mixer (e.g., provided via pump port 218).

[0119] The pump drive can be applied at a frequency difference between the microwave signal and the SAW signal. For example, at 904 of method 900, a first quantum of information can be transferred from a superconducting surface acoustic wave resonator (e.g., superconducting SAW resonator 102) to a superconducting microwave resonator (e.g., superconducting microwave resonator 104), and a second quantum of information can be transferred from the superconducting microwave resonator to the superconducting surface acoustic wave resonator. The transfer of the first quantum of information and the second quantum of information can be enabled by a microwave control signal received by a microwave Josephson mixer. Thus, the same pump frequency and amplitude can be applied to convert the same amount of information in both directions (e.g., from the superconducting surface acoustic wave to the superconducting microwave resonator and from the superconducting microwave resonator to the superconducting surface acoustic wave).

[0120] FIG. 10 is a flow diagram illustrating a method 1000 of operation of a switch used to mix surface acoustic waves and microwave signals based on the frequency and amplitude of a microwave control signal.

[0121] At 1002 of method 1000, the connection between the superconducting surface acoustic wave resonator and the superconducting microwave resonator can be severed (e.g., by microwave Josephson mixer 402 or JRM 106). The disconnection can be based on a first determination to stop mixing of the surface acoustic wave signal and the microwave signal. Thus, communication between the superconducting surface acoustic wave resonator and the superconducting microwave resonator is severed.

[0122] Also, at 1004 of method 1000, the connection between the superconducting surface acoustic wave resonator and the superconducting microwave resonator can be re-enabled (e.g., by microwave Josephson mixer 402 or JRM 106). The re-enabling of the connection can be based on a second determination to resume mixing of the surface acoustic wave signal and the microwave signal. Thus, communication between the superconducting surface acoustic wave resonator and the superconducting microwave resonator is enabled (or connected).

[0123] FIG. 11 is a flow diagram illustrating a method 1100 for mixing a surface acoustic wave and a microwave signal based on the amplitude of the microwave signal.

[0124] At 1102 of method 1100, a surface acoustic wave signal (e.g., SAW signal 404) and a microwave signal (e.g., microwave signal 406) may be received (e.g., by microwave Josephson mixer 402). At 1104 of method 1100, the surface acoustic wave signal and the microwave signal may be mixed (e.g., by microwave Josephson mixer 402). The mixing may be based on a microwave control signal (e.g., microwave control signal 408) received from a microwave source (e.g., provided via pump port 218).

[0125] Also, at 1106, method 1100 may transfer a first portion of quantum information between the superconducting surface acoustic wave resonator and the superconducting microwave resonator (e.g., by microwave Josephson mixer 402) based on a first amplitude of the microwave control signal. At 1108, method 1100 may transfer a second portion of quantum information between the superconducting surface acoustic wave resonator and the superconducting microwave resonator (e.g., by microwave Josephson mixer 402) based on a second amplitude of the microwave control signal. For example, the first amplitude may be used to transfer the first portion of information between the superconducting surface acoustic wave resonator and the superconducting microwave resonator. The second amplitude may be used to transfer the second portion of information between the superconducting surface acoustic wave resonator and the superconducting microwave resonator.

[0126] FIG. 12 is a flow diagram illustrating a method 1200 for lossless frequency conversion between surface acoustic waves and microwave signals.

[0127] At 1202 of method 1200, a surface acoustic wave signal (e.g., SAW signal 404) may be received (e.g., by frequency converter 502). Also, at 1204 of method 1200, a microwave signal (e.g., microwave signal 406) may be received (e.g., by frequency converter 502). At 1206 of method 1200, a lossless frequency conversion may be performed between a first input of a superconducting surface acoustic wave resonator and a second input of a superconducting microwave resonator based on a pump signal received from a microwave source (e.g., by frequency converter 502).

[0128] According to some implementations, a frequency converter can transfer quantum information from a superconducting surface acoustic wave resonator to a superconducting microwave resonator and vice versa based on the frequency and amplitude of a microwave control signal.

[0129] FIG. 13 is a flow diagram illustrating a method 1300 for upconverting between a surface acoustic wave signal and a microwave signal.

[0130] At 1302, a propagating radio frequency signal can be mapped (e.g., by frequency converter 502) to a phonon mode in the superconducting surface acoustic wave resonator. At 1304, the phonon mode can be upconverted to a photon mode in the superconducting microwave resonator by application of a microwave control signal of the microwave source (e.g., by frequency converter 502). The upconversion of the photon mode is enabled by a lossless three-wave mixing interaction. The upconverted microwave signal can propagate upon exiting the superconducting microwave resonator. According to some implementations, the frequency of the microwave control signal can be equal to the absolute value of the difference between the resonant frequency of the superconducting microwave resonator minus the resonant frequency of the SAW resonator.

[0131] FIG. 14 is a flow diagram illustrating a method 1400 for downconverting between surface acoustic wave signals and microwave signals.

[0132] At 1402 of method 1400, a propagating microwave frequency signal can be mapped (e.g., by frequency converter 502) to a photon mode in the superconducting microwave resonator. At 1404 of method 1400, the photon mode can be downconverted to a phonon mode in the superconducting surface acoustic wave resonator by application of a microwave signal from a microwave source (e.g., by frequency converter 502). The photon mode downconversion is enabled by lossless three-wave mixing interactions, and the downconverted surface acoustic wave signal propagates upon exiting the superconducting SAW resonator.

[0133] FIG. 15 is a flow diagram illustrating a method 1500 for non-degenerate parametric amplification of surface acoustic wave and microwave signals.

[0134] At 1502 of method 1500, a first quadrature component of a surface acoustic wave signal entering a first port of the device and a second quadrature component of a microwave signal entering a second port of the device may be amplified (e.g., by a Josephson parametric amplifier 602). In one embodiment, the amplifying may include amplifying the first quadrature component of the surface acoustic wave signal and the second quadrature component of the microwave signal by a defined amplitude gain value (e.g., measured relative to noise or a reference when no microwave control signal is applied to the superconducting device).

[0135] At 1504, the method 1500 may also output a first amplified signal including the first output signal and the frequency-converted first transmit signal via a first output port (e.g., by the Josephson parametric amplifier 602), and output a second amplified signal including the second output signal and the frequency-converted second transmit signal via a second output port. In some implementations, the first output signal may include a first identical-frequency signal reflected at the first port, and the first transmit signal may include a first frequency-converted signal transmitted from the second port to the first port. Also, the second output signal may include a second identical-frequency signal reflected at the second port, and the second transmit signal may include a second frequency-converted signal transmitted from the first port to the second port.

[0136] 16 illustrates a flow chart of an exemplary, non-limiting method 1600 for creating entangled states between phonon and photon modes of a quantum circuit according to one or more embodiments described herein. For the sake of brevity, repeated descriptions of similar elements employed in other embodiments described herein are omitted.

[0137] At 1602, a first input signal including a first frequency can be input to the superconducting surface acoustic wave resonator (e.g., via entanglement component 702). At 1604, a second input signal including a second frequency can be input to the superconducting microwave resonator.

[0138] Also, at 1606, the method 1600 may output (e.g., by the entanglement component 702) an output signal including an entangled signal including an amplified overlap of the input fields (or input signals) entering the superconducting microwave and SAW resonators. For example, the input fields (or input signals) may be a first input signal and a second input signal. The method may include generating an entangled signal of one or more phonons of the surface acoustic wave output by the superconducting surface acoustic wave resonator and one or more microwave photons output by the superconducting microwave resonator.

[0139] A first qubit can be operably coupled to the entanglement component via a superconducting surface acoustic wave resonator. A second qubit can be operably coupled to the entanglement component via a superconducting microwave resonator. In some implementations, the first qubit can be operably coupled to two or more modes. For these implementations, the second qubit can be operably coupled to a single mode. The entangled signal can include entanglement of a phonon mode and a photon mode. In some implementations, the entangled signal can include an amplified overlap of input signals entering the superconducting microwave resonator and the superconducting surface acoustic wave resonator.

[0140] For ease of explanation, the methodologies are depicted and described as a series of acts. It is understood and appreciated that the subject innovation is not limited by the acts depicted and / or the order of acts; for example, acts may occur in various orders, simultaneously, and / or with other acts not shown and described herein. Also, not all acts depicted may be required to implement a methodology in accordance with the disclosed subject matter. Moreover, those skilled in the art will understand and appreciate that the methodologies may also be represented as a series of interrelated states via a state diagram or events. It is further appreciated that the methodologies disclosed below and throughout this specification can be stored on an article of manufacture to facilitate transporting and transferring such methodologies to a computer. As used herein, the term article of manufacture is intended to encompass a computer program accessible from any computer-readable device or storage medium.

[0141] A preferred embodiment of the present invention also includes a method including amplifying, by a Josephson parametric amplifier, a first quadrature component of a surface acoustic wave signal entering a first port of the device and a second quadrature component of a microwave signal entering a second port of the device; and outputting, by the Josephson parametric amplifier, a first amplified signal via a first output port, the first amplified signal including the first output signal and the frequency-converted first transmit signal, and a second amplified signal via a second output port, the second amplified signal including the second output signal and the frequency-converted second transmit signal.

[0142] Preferably, the first output signal includes a first same-frequency signal reflected at the first port, the first transmit signal includes a first frequency-converted signal transmitted from the second port to the first port, the second output signal includes a second same-frequency signal reflected at the second port, and the second transmit signal includes a second frequency-converted signal transmitted from the first port to the second port.

[0143] Preferably, the amplifying includes amplifying the first orthogonal component of the surface acoustic wave signal and the second orthogonal component of the microwave signal by a Josephson parametric amplifier by a defined amplitude gain value.

[0144] A preferred embodiment of the present invention includes a method comprising: inputting, by an entanglement component having a first qubit operatively coupled via the superconducting surface acoustic wave resonator, a first input signal having a first frequency into the superconducting surface acoustic wave resonator; inputting, by an entanglement component having a second qubit operatively coupled via the superconducting microwave resonator, a second input signal having a second frequency into the superconducting microwave resonator; and outputting, by the entanglement component, an output signal including an entangled signal comprising an amplified overlap of input fields entering the superconducting surface acoustic wave resonator and the superconducting microwave resonator.

[0145] Preferably, the method also includes generating, by an entanglement component, an entanglement signal between one or more phonons of the surface acoustic wave output by the superconducting surface acoustic wave resonator and one or more microwave photons output by the superconducting microwave resonator.

[0146] Preferably, the entanglement signal comprises the entanglement of a phonon mode and a photon mode.

[0147] Preferably, the entangled signal comprises an amplified superposition of input signals entering the superconducting microwave resonator and the superconducting surface acoustic wave resonator.

[0148] The above description includes merely examples. It is, of course, not possible to describe every conceivable combination of elements or methodologies for purposes of describing the present invention, but those skilled in the art will recognize that many other combinations and permutations of the present invention are possible. Furthermore, to the extent that terms such as "includes," "has," and "possesses" are used in this specification, claims, appendices, and drawings, these terms are intended to be inclusive, similar to the use of "comprising" when used as a transitional term in a claim. The description of various embodiments of the present invention has been presented for illustrative purposes, but is not intended to be exhaustive or to be limited to the disclosed embodiments of the present invention. Many modifications and variations will be apparent to those skilled in the art without departing from the scope of the present invention. The terms used herein have been chosen to best explain the principles of embodiments of the present invention, or to best explain technical improvements over techniques found in practical applications or on the market, or to enable those skilled in the art to understand the embodiments of the present invention disclosed herein.

Claims

1. receiving, in a microwave Josephson mixer, a surface acoustic wave signal from a superconducting surface acoustic wave resonator, the surface acoustic wave signal including one or more phonons resonating at a first frequency; receiving, in the microwave Josephson mixer, a microwave signal comprising one or more photons resonating at a second frequency from a superconducting microwave resonator; mixing the surface acoustic wave signal and the microwave signal by a Josephson ring modulator coupled between the superconducting surface acoustic wave resonator and the superconducting microwave resonator constituting the microwave Josephson mixer based on a microwave control signal received from a microwave source operably coupled to the Josephson ring modulator of the microwave Josephson mixer.

2. The mixing mapping a propagating radio frequency signal to a phonon mode in the superconducting surface acoustic wave resonator by the microwave Josephson mixer; 2. The method of claim 1, further comprising: upconverting the phonon mode to a photon mode in the superconducting microwave resonator by applying a microwave control signal having a frequency equal to an absolute value of a frequency difference between the resonant frequencies of the superconducting microwave resonator and the superconducting surface acoustic wave resonator, wherein the upconversion of the phonon mode is performed by a Josephson ring modulator, and the upconverted microwave signal propagates through the mappable transmission line upon exiting the superconducting microwave resonator.

3. The mixing mapping a propagating microwave frequency signal to a photon mode in the superconducting microwave resonator by the microwave Josephson mixer; 2. The method of claim 1, further comprising: down-converting, by the microwave Josephson mixer, the photon mode to a phonon mode in the superconducting surface acoustic wave resonator by applying a microwave control signal having a frequency equal to an absolute value of a frequency difference between the resonant frequencies of the superconducting microwave resonator and the superconducting surface acoustic wave resonator, wherein the down-conversion of the photon mode is performed by a Josephson ring modulator, and the down-converted surface acoustic wave signal propagates upon exiting the superconducting surface acoustic wave resonator.

4. 10. The method of claim 1, further comprising transferring information between the superconducting surface acoustic wave resonator and the superconducting microwave resonator by the microwave Josephson mixer based on a frequency and amplitude of a microwave control signal.

5. 10. The method of claim 1, further comprising transferring quantum information between the superconducting surface acoustic wave resonator and the superconducting microwave resonator based on application of a pump drive applied at a frequency difference between the microwave signal and the surface acoustic wave signal by the microwave Josephson mixer.

6. 10. The method of claim 1, further comprising transferring first quantum information from the superconducting surface acoustic wave resonator to the superconducting microwave resonator and transferring second quantum information from the superconducting microwave resonator to the superconducting surface acoustic wave resonator based on the microwave control signal.

7. disconnecting the superconducting surface acoustic wave resonator from the superconducting microwave resonator based on a determination that the mixing of the surface acoustic wave signal and the microwave signal by the microwave Josephson mixer is to be stopped; 2. The method of claim 1, further comprising: re-enabling the connection between the superconducting surface acoustic wave resonator and the superconducting microwave resonator based on a determination to resume the mixing of the surface acoustic wave signal and the microwave signal by the microwave Josephson mixer.

8. transferring, by the microwave Josephson mixer, a portion of quantum information between the superconducting surface acoustic wave resonator and the superconducting microwave resonator, the portion of quantum information being determined based on a first amplitude of the microwave control signal; 7. The method of claim 6, further comprising transferring, by the microwave Josephson mixer, a portion of quantum information between the superconducting surface acoustic wave resonator and the superconducting microwave resonator, the portion of quantum information being determined based on a second amplitude of the microwave control signal.

9. The mixing of the surface acoustic wave signal and the microwave signal comprises:

7. The method of claim 6, comprising converting information carried by the surface acoustic wave signal into the microwave signal in a manner that preserves energy and phase coherence of the quantum signal.

10. 7. The method of claim 6, wherein the mixing of the surface acoustic wave signal with the microwave signal comprises converting information carried by the microwave signal into the surface acoustic wave signal in a manner that preserves energy and phase coherence of quantum signals.

11. a first superconducting qubit capacitively coupled to a superconducting surface acoustic wave resonator; a second superconducting qubit capacitively coupled to the superconducting microwave resonator; a Josephson ring modulator coupled between the superconducting surface acoustic wave resonator and the superconducting microwave resonator.

12. 12. The superconducting device of claim 11, further comprising a pump drive operatively coupled to two adjacent nodes of the Josephson ring modulator via a first coupling capacitor and a second coupling capacitor.

Images