Flux bias for pulse shaping of microwave signals.

Abstract

The technique relates to pulse shaping of microwave signals. In an embodiment, a non-degenerate mixing device receives a signal and a time-varying magnetic flux via an input port. The non-degenerate mixing device uses the signal and the time-varying magnetic flux to generate an output signal on an output port, the output signal having a waveform profile set by the time-varying magnetic flux.

Description

[Technical field]

[0001] The present invention relates generally to methods and structures for superconducting devices, and more particularly to the use of magnetic flux bias for pulse shaping of microwave signals. [Background technology]

[0002] A characteristic of superconducting devices is that they can provide zero electrical resistance at sufficiently low temperatures. To cool the superconducting device to a suitable temperature for operation, a dilution refrigerator or cryogenic device may be employed. In a known configuration, various input and output microwave lines at room temperature are connected to a dilution refrigerator to provide microwave signals to a superconducting device that is maintained at a lower temperature inside the dilution refrigerator. Summary of the Invention

[0003] An embodiment of the present invention is directed to using a magnetic flux bias for pulse shaping of a microwave signal. A non-limiting example of a method includes receiving, by a nondegenerate mixing device, a signal and a time-varying magnetic flux via an input port. The method includes generating, by the nondegenerate mixing device, an output signal on an output port using the signal and the time-varying magnetic flux, the output signal having a waveform profile set by the time-varying magnetic flux.

[0004] A non-limiting example of the method includes receiving, by a circuit, a signal and a time-varying magnetic flux via an input port, the circuit including a first non-degenerate mixing device coupled to a second non-degenerate mixing device, and generating, by the circuit, an output signal on an output port using the signal and the time-varying magnetic flux, the output signal having a waveform profile set by the time-varying magnetic flux.

[0005] A non-limiting example of a method of configuring a circuit includes coupling a non-degenerate mixing device to a magnetic source, where the non-degenerate mixing device is configured to receive a time-varying magnetic flux from the magnetic source via an input port, and configuring the non-degenerate mixing device to generate an output signal on an output port, where the output signal has a waveform profile set by the time-varying magnetic flux.

[0006] A non-limiting example of a method of configuring a circuit includes coupling a first non-degenerate mixing device and a second non-degenerate mixing device in the circuit, where the first non-degenerate mixing device is coupled to a first magnetic source to receive a fixed magnetic flux via an input port and the second non-degenerate mixing device is coupled to a second magnetic source to receive a time-varying magnetic flux via another input port, and configuring the circuit to generate an output signal on an output port, where the output signal has a waveform profile set by the time-varying magnetic flux.

[0007] A non-limiting example of the system includes a first magnetic source coupled to a first portion of the circuit and configured to provide a fixed magnetic flux to the first portion via an input port, the system includes a second magnetic source coupled to a second portion of the circuit and configured to provide a time-varying magnetic flux to the second portion via another input port, the circuit configured to generate an output signal on an output port, the output signal having a waveform profile set by the time-varying magnetic flux.

[0008] Additional technical features and advantages are realized through the techniques of the present invention. Embodiments and aspects of the present invention are described in detail herein and are considered a part of the claimed subject matter. For a better understanding, reference is made to the detailed description and drawings.

[0009] The particulars of the exclusive rights set forth herein are particularly pointed out and distinctly claimed in the claims at the end of the specification. The foregoing and other features and advantages of embodiments of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic diagram of a circuit in accordance with one or more embodiments of the present invention. [Diagram 2] 1 is a block diagram of a circuit in accordance with one or more embodiments of the present invention. [Diagram 3] 1 is a block diagram of a circuit in accordance with one or more embodiments of the present invention. [Figure 4] 1 is a schematic diagram of a circuit in accordance with one or more embodiments of the present invention. [Diagram 5] FIG. 1 is a block diagram according to one or more embodiments of the present invention. [Figure 6] FIG. 1 is a block diagram according to one or more embodiments of the present invention. [Figure 7] FIG. 1 is a block diagram of a system in accordance with one or more embodiments of the present invention. [Figure 8] FIG. 1 is a block diagram of a system in accordance with one or more embodiments of the present invention. [Figure 9] FIG. 2 is a signal flow diagram for a non-degenerate three-wavemixing device in frequency conversion in accordance with one or more embodiments of the present invention. [Figure 10A] FIG. 2 illustrates a non-degenerate three-wave mixing device in differential mode in accordance with one or more embodiments of the present invention. [Figure 10B] FIG. 2 illustrates a non-degenerate three-wave mixing device in differential mode in accordance with one or more embodiments of the present invention. [Figure 10C] FIG. 2 illustrates a non-degenerate three-wave mixing device in common mode in accordance with one or more embodiments of the present invention. [Figure 11]1 is a flow chart of a method for pulse shaping in accordance with one or more embodiments of the present invention. [Figure 12] 1 is a flow chart of a method for pulse shaping in accordance with one or more embodiments of the present invention. [Figure 13] 1 is a flow chart of a method of configuring a circuit in accordance with one or more embodiments of the present invention. [Figure 14] 1 is a flow chart of a method of configuring a circuit in accordance with one or more embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The figures shown herein are illustrative. There may be many variations to the figures or the operations described therein without departing from the spirit of the invention. For example, actions may be performed in a different order, or actions may be added, deleted, or modified. Also, the term "coupled" and variations thereof refer to having a communication path between two elements, and do not imply a direct connection between elements without an intervening element / connection between them. All of these variations are considered part of the specification.

[0012] In the accompanying drawings and the following detailed description of embodiments of the invention, various elements illustrated in the drawings are given two or three digit reference numbers. With few exceptions, the leftmost digit of each reference number corresponds to the drawing in which the element is first shown.

[0013] One or more embodiments of the present invention provide techniques and devices that perform pulse shaping of a continuous wave microwave signal inside a cooling system. In some embodiments of the present invention, the cooling system includes a dilution refrigerator. One or more embodiments of the present invention perform pulse shaping of a microwave signal in proximity to a quantum device. In some embodiments of the present invention, a quantum processor in proximity to the microwave signal to be pulse shaped is inside the cooling system. Because generating microwave signals using room temperature electronics and transmitting these signals through microwave lines to a superconducting device can result in various degradation issues, one or more embodiments of the present invention can avoid such degradation issues associated with transmitting a microwave signal from room temperature to the base stage temperature of a dilution refrigerator because the pulse shaping of the microwave signal occurs inside the cooling system in proximity to one or more quantum devices.

[0014] Turning now to a more detailed description of aspects of the invention, FIG. 1 illustrates a schematic diagram of a circuit 100 for a nondegenerate parametric device 102 in accordance with one or more embodiments of the invention. The nondegenerate parametric device 102 is illustrated as an example Josephson parametric converter (JPC). The nondegenerate parametric device 102 is constructed to amplify and / or mix microwave signals at the quantum limit. The nondegenerate parametric device 102 includes a Josephson ring modulator (e.g., JRM) 104 integrated into two microwave resonators 110 (e.g., resonator a) and 112 (e.g., resonator b) at antinodes of a fundamental eigenmode rf current (i.e., radio frequency current). The JRM 104 is a nonlinear dispersive element including a Josephson tunnel junction 106 that can perform three-wave mixing of microwave signals at the quantum limit. The JRM 104 has four nominally identical Josephson junctions 106 arranged in a four-node Wheatstone bridge configuration. The performance of the JRM 104, i.e., power gain, dynamic bandwidth, and dynamic range, strongly depends on the critical currents of the Josephson junctions 106 of the JRM 104, the particular realization of the electromagnetic environment (i.e., microwave resonators 110 and 112), and the coupling between the JRM 104 and the resonators 110 and 112.

[0015] 1, one end of a resonator 110 (e.g., resonator a) is coupled to a port 150 (e.g., port a) via a coupling capacitor 114A and a transmission line 116, and the other end of the resonator 110 is coupled to ground via a coupling capacitor 114A and a transmission line 116. One end of a resonator 112 (e.g., resonator b) is coupled to a port 160 (e.g., port b) via a coupling capacitor 114B and a transmission line 116, and the other end of the resonator 112 is coupled to ground via a coupling capacitor 114B and a transmission line 116. The resonator 110 has a resonant frequency f a and the resonator 112 has a resonant frequency f b where f a f b . The pump port 170 (e.g., port P) couples to the JRM 104 via a flux line 120. The flux line 120 may include a shorted loop 122 that capacitively couples to the JRM 104, thereby forming a shorted coplanar stripline. The flux line 120 may be a lossless on-chip flux line that capacitively couples to two adjacent nodes of the JRM 104's four nodes. The pump port 170 differentially couples to the two adjacent nodes of the JRM 104 at a frequency f p The non-degenerate parametric device 102 receives a pump microwave signal (e.g., a pump drive), where the pump drive signal induces a common mode in the non-degenerate parametric device 102 (e.g., a JPC).

[0016] The controlled magnetic source 182 provides an external magnetic flux bias to the JRM 104 by generating a magnetic field (e.g., a B field, or magnetic flux density) based on a current (I). A port 180 (e.g., port M) is shown as an example of the JRM 104 receiving the external magnetic flux. The example location of the port 180 is given for illustrative purposes and is not meant to be limiting. In accordance with one or more embodiments of the present invention, the magnetic source 182 is configured to generate and provide a time-varying or pulsed magnetic flux to the JRM 104. The applied magnetic field is varied (e.g., by applying a current (e.g., a direct current or an alternating current) to a superconducting coil) and then converted to an applied magnetic flux. The magnetic flux (Φ ext ) is a physical quantity that represents the amount of magnetic field passing through the superconducting loop (i.e., JRM 104). While FIG. 1 shows magnetic source 182 to be external to chip 190, it should be understood that magnetic source 182 may be implemented in other ways and may be on-chip in one or more embodiments of the present invention. In some examples, the external magnetic flux may be applied using on-chip magnetic flux lines, external magnetic coils (e.g., magnetic source 182), or may be applied using magnetic material integrated on-chip or within the chip package.

[0017] Although FIG. 1 shows a microstrip implementation of the non-degenerate parametric device 102 as a JPC on a chip 190, the non-degenerate parametric device 102 is not meant to be limited and other implementations are contemplated. The non-degenerate parametric device 102 may be implemented using coplanar stripline resonators, microstrip resonators (as shown in FIG. 1), compact / lumped element resonators, impedance matching networks, lumped element capacitors and inductors, and three-dimensional cavities. Additionally, the dynamic range of the non-degenerate parametric device 102 (e.g., a JPC) may be improved by extending the critical current of the Josephson junctions 106 forming the JRM 104, for example, by using niobium junctions and nanobridges. The tuning bandwidth of the non-degenerate parametric device 102 may be increased by shunting the Josephson junctions 106 of the JRM 104 with a linear inductance, such as using a shunted Josephson junction 108 in a ring. Also, the instantaneous bandwidth of the non-degenerate parametric device 102 can be extended by coupling the JRM 104 to an external feedline through a properly designed impedance matching network, allowing the device to operate on fast time scales and support steep pulses.

[0018] 1 is depicted diagrammatically as a superconducting magnetic coil, it should be noted that the magnetic source 182 may be realized as on-chip magnetic flux lines and / or magnetic flux lines realized on a flip chip in the vicinity of the JRM, and that they are driven by DC and AC currents. Additionally, it should be noted that there should be a relatively strong mutual inductance between the magnetic source 182 and the JRM 104.

[0019] The microwave resonators 110 and 112, the transmission line 116, the transmission line 124, the Josephson junctions 106 and 108, the JRM 104, and the magnetic flux lines 120 comprise a superconducting material that exhibits superconductivity below a critical temperature.

[0020] FIG 2 shows an example of pulse shaping using frequency conversion by circuit 100 in accordance with one or more embodiments of the present invention. The non-degenerate parametric device 102 may be a lossless JPC operating in full frequency conversion mode with harmonic suppression. FIG 2 and FIG 3 (described below) incorporate details of FIG 1, but details are omitted for brevity and so as not to obscure FIG 2 and FIG 3.

[0021] In FIG. 2, the non-degenerate parametric device 102 outputs a continuous wave / signal having a frequency f1 at a port 150 (e.g., port a) and a continuous wave / signal having a frequency f p The non-degenerate parametric device 102 receives a time-varying or pulsed magnetic flux at a port 180 (e.g., port M). In this example, the time-varying magnetic flux is shown as, for example, a repeating rectangular pulse with a magnitude from 0 to B1. The value 0 is shown for illustrative purposes, and the magnitude may vary between any value including between B1 and a non-zero value. The non-degenerate parametric device 102 is configured to generate an output signal having a frequency f2 and having a shaped pulse or waveform based on the time-varying magnetic flux input at the port 180. For an input signal at frequency f1 and an output signal at frequency f2, a pump signal (at frequency f p ) is f p =|f2-f1|. Unlike diode-based mixers, the operating point of the non-degenerate parametric device 102 (e.g., JPC) depends on the applied magnetic flux bias from the magnetic source 182. By varying the applied magnetic flux as a function of time, the non-degenerate parametric device 102 is configured to modulate the microwave signal transmitted through the non-degenerate parametric device 102, thereby resulting in a modulated pulse or waveform shape for the output signal at frequency f2 via frequency conversion.

[0022] The magnetic source 182 may be controlled by and coupled to a controller (not shown) to generate a time-varying magnetic flux for the port 180. An example controller may include or be coupled to a current source configured to provide a time-varying current, such as, for example, a DC current and an AC current. The controller may include a processor configured to read / execute computer-executable instructions in a memory. Based on the execution of the instructions, the controller is configured to cause the current source to vary the current provided to the magnetic source 182, which in turn generates a time-varying magnetic flux (e.g., a pulsed magnetic flux) according to one or more embodiments of the present invention.

[0023] In this example, FIG. 2 shows a square wave as the time varying flux. It is contemplated that different types of time varying flux may be utilized to pulse shape the corresponding output signal (frequency f2). Examples of types of time varying flux may include a square pulse (e.g., shown in FIG. 2), a sinc pulse, a Gaussian pulse (e.g., shown in FIG. 3), a raised cosine pulse, etc.

[0024] 3 illustrates pulse shaping using frequency conversion by circuit 100 in accordance with one or more embodiments of the present invention. In FIG. 3, non-degenerate parametric device 102 may be a lossless JPC operating in full frequency conversion mode with harmonic suppression. Non-degenerate parametric device 102 provides a continuous wave / signal with frequency f1 at port 150 (e.g., port a) and a continuous wave / signal with frequency f1 at port 170 (port P). pAs discussed herein, the non-degenerate parametric device 102 receives a time-varying or pulsed magnetic flux at a port 180 (e.g., port M). In this example, the time-varying magnetic flux is shown as a Gaussian pulse with a magnitude that varies from 0 to B1. The non-degenerate parametric device 102 is configured to generate an output signal having a frequency f2 and having a shaped pulse or waveform based on the time-varying magnetic flux input at the port 180, as shown in FIG. 3. It should be noted that the Gaussian shape of the flux modulation shown in FIG. 3 is an exemplary simplification of the actual pulse shape required to generate a Gaussian pulse of the microwave signal at the output. The actual required shape can be mathematically calculated using the device time response (versus time) as a function of the applied magnetic flux. Again, for an input signal of frequency f1 and an output signal of frequency f2, the pump signal (frequency f p ) is f p =|f2-f1|=|f b -f a The application is made so as to satisfy the relationship |.

[0025] 2 and 3, in addition to shaping the pulses of the output signal, also uses frequency conversion to convert the input frequency f1 of the input signal at port 150 to the output frequency f2 of the output signal at port 160. Although this embodiment is shown with up-conversion, down-conversion may be performed as well.

[0026] There are various technical benefits of performing pulse shaping or wave shaping of microwave signals by superconducting circuits (e.g., circuit 100 and circuit 400 described below) in a cooling system. The superconducting circuits are in proximity to one or more quantum processors that receive the pulse shaped microwave signals in the cooling system. Generating microwave signals / pulses (which may be qubit readout and qubit control signals) using room temperature electronics and transmitting them over microwave lines to a superconducting quantum processor located in a dilution refrigerator has several problems. These problems may be avoided and / or mitigated by one or more embodiments of the present invention, but are not required. Exemplary problems that may be avoided and / or mitigated by one or more embodiments of the present invention include the following: Due to various impedance mismatches and dispersion relationships (i.e., frequency dependence) in the input lines of a dilution refrigerator, which typically include coaxial cables, microwave connectors, filters, attenuators, and microwave components, the transmitted microwave pulses are distorted on the path to the quantum processor. These distortions can cause single-qubit and two-qubit gate errors in the readout, which may, but need not, be avoided and / or mitigated by one or more embodiments of the present invention due to the pulse shaping that occurs internally to the cooling system. Furthermore, it should be noted that these distortions may be difficult to measure and characterize when the dilution refrigerator is at room temperature, since the responses of these microwave components tend to change when cooled.

[0027] Another example problem that may be avoided and / or mitigated by one or more embodiments of the present invention includes the following: Diode-based mixers used to generate microwave pulses at room temperature tend to create parasitic harmonics and sidebands that can cause readout and gating errors for the quantum processor if not suppressed or filtered, at the cost of adding overhead to the setup. However, these and other problems may be avoided and / or mitigated by one or more embodiments of the present invention, but are not required. Additional example problems that may be avoided and / or mitigated by one or more embodiments of the present invention include the following: To shield the readout resonator of the quantum processor from elevated thermal photon distribution due to noise traveling through the readout input lines (which may lead to qubit dephasing), intensity filtering and attenuation are built into these lines to attenuate the thermal noise at these relatively high frequencies (e.g., 7 gigahertz (GHz) and above) of the readout resonator. This also adds hardware overhead to the setup. However, because the radio frequencies are generated within the cooling system rather than externally at room temperature, these and other problems may be avoided and / or mitigated by one or more embodiments of the present invention, but are not required.

[0028] FIG 4 shows a schematic diagram of a circuit 400 for coupling non-degenerate parametric devices according to one or more embodiments of the present invention. In FIG 4 (along with FIG 5 and FIG 6), the non-degenerate parametric device includes details of the non-degenerate parametric device 102 of FIG 1, and the two non-degenerate parametric devices are shown as non-degenerate parametric devices 102_1 and 102_2, although their structures are nominally identical. Some details of the non-degenerate parametric device 102 of FIG 1 are not shown in FIG 4, FIG 5, and FIG 6 for brevity, but apply by analogy.

[0029] In FIG. 4, the non-degenerate parametric devices 102_1 and 102_2 each include their own JRM 104 embedded in two microwave resonators 110 (e.g., resonator a) and 112 (e.g., resonator b) at the rf current antinodes of the fundamental eigenmode. As described above, each JRM 104 includes a Josephson tunnel junction 106. In the non-degenerate parametric device 102_1 of the circuit 400, one end of the resonator 110 (e.g., resonator a) is coupled to a port 150_1 (e.g., port a) via a coupling capacitor 114A and a transmission line 116, and the other end of the resonator 110 is coupled to ground via a coupling capacitor 114A and a transmission line 116. In the non-degenerate parametric device 102_1, one end of the resonator 112 (e.g., resonator b) is coupled to a port 160_1 (e.g., port b) via a coupling capacitor 114B and a transmission line 116, and the other end of the resonator 112 is coupled to ground via a coupling capacitor 114B and a transmission line 116. The non-degenerate parametric device 102_1 is coupled to a pump port 170_1 via magnetic flux lines 120.

[0030] Similarly, in the non-degenerate parametric device 102_2 of the circuit 400 of FIG. 4, one end of the resonator 110 (e.g., resonator a) is coupled to a port 150_2 (e.g., port a) via a coupling capacitor 114A and a transmission line 116, and the other end of the resonator 110 is coupled to ground via a coupling capacitor 114A and a transmission line 116. In the non-degenerate parametric device 102_2, one end of the resonator 112 (e.g., resonator b) is coupled to a port 160_2 (e.g., port b) via a coupling capacitor 114B and a transmission line 116, and the other end of the resonator 112 is coupled to ground via a coupling capacitor 114B and a transmission line 116. The non-degenerate parametric device 102_2 is coupled to a pump port 170_2 via a magnetic flux line 120. Ports 160_1 and 160_2 (port b) are shared by both non-degenerate parametric devices 102_1 and 102_2 (eg, JPCs are back-to-back).

[0031] Similar to FIG. 1, the non-degenerate parametric devices 102_1 and 102_2 in the circuit 400 of FIG. 4 transmit magnetic flux (Φ ext ) separately. FIG. 4 illustrates a magnetic source 182_1 providing an external flux bias to the JRM 104 via port 180_1 in the non-degenerate parametric device 102_1 by generating a magnetic field (e.g., a B-field or magnetic flux density) based on a current (I). Similarly, FIG. 4 illustrates a magnetic source 182_2 providing an external flux bias to the JRM 104 in the non-degenerate parametric device 102_2 via port 180_2. FIG. 4 illustrates a circuit 400 on a chip 190. Although FIG. 4 illustrates a microstrip implementation of the non-degenerate parametric devices 102_1 and 102_2, the non-degenerate parametric devices 102_1 and 102_2 are not meant to be limiting and other implementations are possible as described herein.

[0032] 5 illustrates pulse shaping without frequency conversion (when comparing the frequency of the input signal to the output signal) in accordance with one or more embodiments of the present invention. The non-degenerate parametric device 102_1 outputs a continuous wave / signal having a frequency f1 at port 150_1 (e.g., input port a of the circuit 400) and a continuous wave / signal having a frequency f1 at port 170_1 (port P). p The non-degenerate parametric device 102_2 receives a continuous wave / signal having a frequency f p5. Hybrid coupler 502 is connected to circuit 400 via pump ports 170_1 and 170_2. The opposite end of hybrid coupler 502 is connected to port 504 which receives the pump signal before distributing it to pump ports 170_1 and 170_2 and is connected to port 506. Port 506 may be coupled to a low temperature terminal, for example a standard 50 ohm (Ω) terminal. Hybrid coupler 502 is shown as a 90° (degree) hybrid coupler, it should be understood that other types of couplers may be utilized. Ports 170_1 and 170_2 each receive one-half the magnitude of the pump signal for hybrid coupler 502. In one or more embodiments of the present invention, hybrid coupler 502 may be omitted and pump ports 170_1 and 170_2 may receive their pump signals separately.

[0033] Returning to the example of FIG. 5, the non-degenerate parametric device 102_1 receives a fixed magnetic flux at a port 180_1 (e.g., port M). The fixed magnetic flux does not change over time, and therefore its magnitude (B1) remains unchanged. It is understood that the magnitude of the fixed magnetic flux is intended to remain constant and / or nearly constant over time, but the magnitude is constant within the tolerances of the equipment generating the magnetic flux, and variations due to errors are allowed. However, the non-degenerate parametric device 102_2 receives a time-varying or pulsed magnetic flux at a port 180_2 (e.g., port M), where the magnitude at port 180_2 varies over time, for example from 0 to B1. In this example, the time-varying magnetic flux is shown as a rectangular pulse.

[0034] The non-degenerate parametric device 102_1 outputs the frequency-converted signal at the port 160_1 (port b) to the port 160_2 of the non-degenerate parametric device 102_2. As described herein, the ports 160_1 and 160_2 are shared ports of the non-degenerate parametric devices 102_1 and 102_2 of FIG. 5. The frequency-converted signal may be an up-conversion or down-conversion or both of the input signal (f1) received at the port 150_1 of the non-degenerate parametric device 102_1. In this embodiment, the frequency of the input signal is up-converted to a signal at frequency f2 and transmitted to the non-degenerate parametric device 102_2. This converted signal at frequency f2 is an intermediate signal.

[0035] In response to receiving the frequency translated signal at port 160_2, the non-degenerate parametric device 102_2 is configured to generate an output signal having a frequency f1 and having a shaped pulse or waveform based on the time-varying flux input at port 180_2 (port M). For an input signal of frequency f1 and an output signal of frequency f1, assuming the frequency translated signal has a frequency f2, the pump signal (frequency f p ) is f p =|f2-f1|. As described herein, the operating points of the non-degenerate parametric devices 102_1 and 102_2 (e.g., JPCs) depend on the applied flux biases. By maintaining a fixed flux for the non-degenerate parametric device 102_1 and varying the applied flux as a function of time for the non-degenerate parametric device 102_2, the non-degenerate parametric devices 102_1 and 102_2 are configured to modulate the input microwave signal transmitted through the non-degenerate parametric devices 102_1 and 102_2, thereby resulting in a modulated pulse or waveform shape for the output signal at frequency f1.

[0036] The magnetic sources 182_1 and 182_2 may be controlled to generate a fixed magnetic flux for the port 180_1 and a time-varying magnetic flux for the port 180_2, respectively, using one or more controllers coupled to one or more current sources. In one or more embodiments of the present invention, each magnetic source 182_1 and 182_2 may be coupled to its own controller and / or current source. Additionally, the controller may control a current source having multiple outputs to provide current to the magnetic sources 182_1 and 182_2 independently. FIG. 5 illustrates a square wave as the time-varying magnetic flux. As described herein, different types of time-varying magnetic flux may be utilized to pulse shape the corresponding output signal while maintaining the frequency f1. Example types of time-varying magnetic flux may include a square pulse (e.g., shown in FIG. 5), a sinc pulse, a Gaussian pulse (e.g., shown in FIG. 6), a raised cosine (cosine squared) pulse, etc.

[0037] 6 illustrates pulse shaping with frequency preservation by circuit 400 in accordance with one or more embodiments of the present invention. In FIG. 6, non-degenerate parametric devices 102_1 and 102_2 are similar to FIG. 5, and some details may be omitted. Non-degenerate parametric device 102_1 provides a continuous wave / signal with frequency f1 at port 150_1 (e.g., input port a of circuit 400) and a continuous wave / signal with frequency f1 at port 170_1 (port P). p The non-degenerate parametric device 102_2 receives a continuous wave / signal having a frequency f p Receives a continuous wave / signal having

[0038] As described herein, the non-degenerate parametric device 102_1 receives a fixed magnetic flux at a port 180_1 (e.g., port M), which does not change over time and therefore its magnitude (B1) remains unchanged. The non-degenerate parametric device 102_2 receives a time-varying or pulsed magnetic flux at a port 180_2 (e.g., port M), which has a magnitude that varies over time, e.g., from 0 to B1, at port 180_2. In this example, the time-varying magnetic flux is shown as a Gaussian pulse.

[0039] The non-degenerate parametric device 102_1 outputs a frequency-converted signal at port 160_1 (port b) to port 160_2 of the non-degenerate parametric device 102_2. The frequency-converted signal may be an up-conversion and / or down-conversion of an input signal (f1) received at port 150_1 of the non-degenerate parametric device 102_1. For example, an input signal at frequency f1 may be up-converted to frequency f2 and transmitted to the non-degenerate parametric device 102_2 as a frequency-converted signal. In response to receiving the frequency-converted signal at port 160_2, the non-degenerate parametric device 102_2 is configured to generate an output signal having frequency f1 and having a shaped pulse or waveform based on a time-varying flux input at port 180_2 (port M). For an input signal at frequency f1 and an output signal at frequency f1, assuming the frequency-converted signal is at frequency f2, the pump signal (at frequency f1) may be up-converted to frequency f2 and transmitted to the non-degenerate parametric device 102_2 as a frequency-converted signal. p ) is f p By maintaining a fixed magnetic flux for non-degenerate parametric device 102_1 and varying the applied magnetic flux as a function of time for non-degenerate parametric device 102_2, non-degenerate parametric devices 102_1 and 102_2 are configured to modulate the input microwave signal transmitted through non-degenerate parametric devices 102_1 and 102_2, thereby resulting in a modulated pulse or waveform shape for the output signal at frequency f1.

[0040] 5 and 6 show an example where the non-degenerate parametric device 102_1 receives a fixed magnetic flux at port 180_1 and the non-degenerate parametric device 102_2 receives a time-varying magnetic flux at port 180_2, it should be understood that other architectures are possible. According to one or more embodiments of the present invention, the phase and / or amplitude of the output signal (e.g., frequency f1) in the circuit 400 may be modulated with the frequency of the time-varying magnetic flux. In this example, the non-degenerate parametric device 102_1 receives a time-varying magnetic flux at port 180_1 and the non-degenerate parametric device 102_2 receives a fixed magnetic flux at port 180_2, which means that the external biases applied to ports 180_1 and 180_2, respectively, are opposite. As a result, the transmitted output signal at port 150_2 of non-degenerate parametric device 102_2 may have its phase and / or amplitude modulated according to the frequency of the time-varying magnetic flux received by non-degenerate parametric device 102_1 at port 180_1. Circuit 400 may be coupled to a receiver (not shown) such that the transmitted output signal is transmitted from circuit 400 to the receiver, thereby enabling circuit 400 to be utilized for microwave communications.

[0041] FIG. 7 illustrates a system 700 that utilizes circuit 100 to generate and pulse shape quantum signals (e.g., readout and / or qubit signals) in situ (e.g., within a cooling system) in accordance with one or more embodiments of the present invention. System 700 includes circuit 100 coupled to a quantum processor 702 in a cooling system, such as a dilution refrigerator. Quantum processor 702 may include a plurality of superconducting qubits, a readout resonator, a quantum memory, and a quantum coupling device. Quantum processor 702 includes a qubit 710 coupled to a readout resonator 712. A resonator is a physical assembly having multiple energy levels that may be used to store all or a portion of a qubit's information. For example, a resonator may be implemented as a transmission line, a resonating cavity, or any other structure suitable for a given application. Generally, a resonator has a characteristic frequency that is constant, but it should be understood that a tunable resonator assembly may be used if required by a given application. A qubit is a physical assembly with multiple energy states whose distribution can be controlled. A qubit can be implemented, for example, as an anharmonic oscillator that can transfer energy between some combination of the electric field of a capacitor, the magnetic field of an inductor, and a superconducting phase difference. Example implementations of a qubit may include one or more of a Josephson junction, a linear inductor, a superconducting loop, a gap capacitance, and a plate capacitance, which can be realized, for example, as a Cooper pair box qubit, a transmon qubit, a fluxonium qubit, and a flux qubit.

[0042] 7, one or more readout resonators 712 are configured to infer or read out the state of one or more qubits 710. The readout resonators 712 are configured to receive a readout signal / pulse that causes the readout resonators 712 to encode their state information corresponding to the state of the one or more qubits 710 into an output readout signal exiting the quantum processor 702. The circuit 100 is configured to generate and pulse shape the readout signal, which is an output signal from a port 160 (e.g., port b) of the non-degenerate parametric device 102.

[0043] Using the output signal from port 160 of non-degenerate parametric device 102 as a readout signal / pulse for quantum processor 702 provides various benefits to system 700. A readout pulse of frequency f2 is generated at f1 and f2. p Because the system 700 is generated by feeding a continuous wave of f2 to the non-degenerate parametric device 102 (e.g., JPC) and by a time-varying magnetic flux (e.g., using DC and / or AC currents), the resulting pulse (i.e., output signal) is close to the quantum processor 702 (e.g., within the same cooling system), thereby avoiding (or suffering little from) the distortion and unwanted harmonics associated with a readout pulse generated with room temperature electronics (external to the cooling system). In particular, the system 700 avoids the distortion and unwanted harmonics associated with a readout pulse generated with room temperature electronics and transmitted through a dilution refrigerator input line that includes multiple attenuators, filters, microwave cables, and connectors. Due to various difficult-to-avoid impedance mismatches and frequency dispersion, the multiple attenuators, filters, microwave cables, and connectors can all potentially distort the readout pulse propagating down the line at frequency f2 before reaching the quantum processor. The room temperature electronics are connected to the cooling system by an input line that begins at room temperature and terminates inside the cooling system. In FIG. 7, the transmission line connecting the circuit 100 and the quantum processor 702 is within the cooling system.

[0044] Furthermore, frequencies f1 and f p The relatively low frequency microwave signal of f2, as well as the time varying magnetic flux, is easier and cheaper to generate and control compared to the high frequency microwave signal of frequency f2 that is typically generated at room temperature. Thus, by having circuit 100 generating an output signal of frequency f2 in a cooling system along with quantum processor 702, system 700 reduces the thermal photon distribution inside readout resonator 712 that causes qubit dephasing. Although one circuit 100 coupled to quantum processor 702 is shown in FIG. 7, it should be understood that multiple circuits 100 may be coupled to quantum processor 702.

[0045] FIG. 8 illustrates a system 800 that utilizes circuit 400 to generate and pulse shape a quantum signal (e.g., a readout signal and / or a qubit signal) in situ (e.g., within a cooling system) in accordance with one or more embodiments of the present invention. System 800 includes circuit 400 coupled to a quantum processor 702 in a cooling system, such as a dilution refrigerator. As described herein, quantum processor 702 includes one or more qubits 710 coupled to a readout resonator 712. The state of one or more qubits 710 may be affected or altered based on receiving a qubit signal / pulse, which may be a signal at or around the resonant frequency of qubit 710. Circuit 400 is configured to generate and pulse shape a qubit signal (and / or a readout signal), which is an output signal from port 150_2 of non-degenerate parametric device 102_2.

[0046] A qubit signal / pulse of frequency f (e.g., corresponding to an output signal) is a continuous wave of frequency f at port 150_1 and a pulse of frequency f at pump ports 170_1 and 170_2. pqubit pulses are generated by feeding a continuous wave of qubits, a fixed flux at port 180_1, and a time-varying flux at port 180_2, to two non-degenerate parametric devices 102_1 and 102_2 (e.g., two JPCs), respectively, such that the resulting pulses (i.e., output signals) are in close proximity (e.g., within the same cooling system) to the quantum processor 702, and thus the output signals to the quantum processor 702 avoid (or suffer little from) the distortions and unwanted harmonics associated with qubit pulses generated using room temperature electronics that are external to the cooling system. Although one circuit 400 coupled to the quantum processor 702 is shown in FIG. 8, it should be understood that multiple circuits 400 may be coupled to the quantum processor 702.

[0047] As described herein, system 800 avoids distortions and unwanted harmonics associated with qubit pulses generated using room temperature electronic components and transmitted through a dilution refrigerator input line that includes multiple attenuators, filters, microwave cables, and connectors, all of which can potentially distort the qubit pulses propagating down the line at frequency f1 before reaching the quantum processor due to various difficult to avoid impedance mismatches and frequency dispersion along the long line. System 800 is thus configured to provide better single-qubit and two-qubit gate fidelity at quantum processor 702.

[0048] To aid the reader's understanding and for the sake of limitation, further details regarding the non-degenerate parametric device 102 are described below in Figures 9, 10A, 10B, and 10C. Figure 9 illustrates a signal flow diagram for a non-degenerate three-wave mixing device in frequency conversion according to one or more embodiments of the present invention. The superconducting non-degenerate three-wave mixing device has three ports, generally designated as a signal port (S) (e.g., port a), an idler port (I) (e.g., port b), and a pump port (e.g., pump P). The superconducting non-degenerate three-wave mixing device has a transmission t from the idler port to the signal port and a transmission t' from the signal port to the idler port. From the idler to the signal port, the idler microwave signal enters the idler port at frequency f2, is down-converted, and exits the signal port at frequency f1. From the signal to the idler port, a signal microwave signal enters the signal port at frequency f1, is upconverted, and exits the idler port at frequency f2. The pump microwave signal provides the energy for frequency upconversion and frequency downconversion. The pump frequency is f p where f p =f2-f1=f b -f a It is.

[0049] A superconducting non-degenerate three-wave mixing device such as a JPC satisfies the following scattering matrix for resonance when operated in noiseless frequency conversion:

[0050]

number

number

[0051] The perfect conversion operating point is perfect transmission with no reflection and frequency conversion, |r| 2 =0, |t| 2 = 1. Because the scattering matrix is ​​unitary, the following relation holds: |r| 2 +|t| 2 = 1. Unitary preserves the energy and phase coherence of the transmitted signal. The JPC is a three-wave mixing device that contains three modes: differential mode X shown in Figure 10A, differential mode Y shown in Figure 10B, and common mode Z shown in Figure 10C.

[0052] Figures 10A, 10B, and 10C show the rf voltage excitation patterns for modes X, Y, and Z of the JRM. The coupling constant g3 between these three modes is related to the Josephson energy E of the outer Josephson junction of the JRM. j , which depends on the frequencies of modes X, Y, and Z, and the participation ratios of the three modes, which corresponds to the ratio of the Josephson junction (JJ) inductance to the total inductance of the resonant mode structure, as well as the magnetic flux (Φ ext ) The Josephson energy of JJ depends on E j The linear inductor shunting JJ is denoted as L.

[0053] In Figures 10A, 10B, and 10C, the sign of the coupling constant g3 corresponds to the circulating current I circ Depending on the direction of the external magnetic flux (Φ ext When a pump drive (e.g., a strong coherent microwave tone) is applied to the JPC, the coupling constant between modes a and b of the JPC depends on

number

[0054] Further explanation is given regarding the inductively shunted JRM energy.

number

[0055]

number

number

number

number

[0056] E JRM In the formula (JRM Energy),

number

number

number

number

number

number

number

number

[0057] 11 is a flow chart of a method 1100 for pulse shaping using frequency conversion, according to one or more embodiments. The method 1100 includes, at block 1102, receiving a signal and a time-varying magnetic flux (e.g., via port 180 (port M)) by a mixing device (e.g., non-degenerate parametric device 102). At block 1104, the mixing device (e.g., non-degenerate parametric device 102) is configured to use the signal and the time-varying magnetic flux to generate an output signal (e.g., via port 160) having a waveform profile set by the time-varying magnetic flux.

[0058] The signals include a first microwave signal (e.g., an input signal at frequency f1) and a second microwave signal (e.g., an input signal at frequency f p The mixing device includes a pump signal (e.g., via port 180) and the first microwave signal and the second microwave signal are at different frequencies. The time-varying magnetic flux (e.g., via port 180) is a time-varying control signal having a magnitude that is modulated as a function of time. The microwave signal is a continuous wave signal whose amplitude, frequency, and phase are fixed over time. The mixing device includes a ring modulator (e.g., Josephson ring modulator 104). A waveform profile of the output signal (e.g., an output signal at frequency f2) is generated based at least in part on the ring modulator of the mixing device in response to the time-varying magnetic flux.

[0059] FIG. 12 is a flow chart of a method 1200 for pulse shaping without frequency conversion (i.e., the frequencies of the output signal and the input signal are equal (or substantially equal)), according to one or more embodiments. At block 1202, the method 1200 includes receiving, by a circuit (e.g., circuit 400), a signal (e.g., via a port), where the circuit includes a first mixing device (e.g., non-degenerate parametric device 102_1) coupled to a second mixing device (e.g., non-degenerate parametric device 102_2). At block 1204, the circuit (e.g., circuit 400) is configured to use the signal (e.g., via ports 150_1, 150_2, 170_1, 170_2) and the time-varying magnetic flux (via port 180_2) to generate an output signal having a waveform profile set by the time-varying magnetic flux.

[0060] The time-varying magnetic flux is a time-varying signal having a magnitude modulated as a function of time. One of the first mixing device and the second mixing device receives the time-varying magnetic flux, and the other of the first mixing device and the second mixing device receives the fixed magnetic flux. The first mixing device (e.g., the non-degenerate parametric device 102_1) is configured to provide an intermediate signal (e.g., the transformed signal via port 160_1) to the second mixing device (e.g., the non-degenerate parametric device 102_2) using a first signal (e.g., the input signal via port 150_1) and a second signal (e.g., the pump signal via port 170_1) of the signals. The second mixing device is configured to receive the intermediate signal from the first mixing device, and the second mixing device is configured to generate an output signal (e.g., the output signal via port 150_2) using the intermediate signal (e.g., the transformed signal) as an input.

[0061] 13 is a flow chart of a method 1300 of configuring the circuit 100, according to one or more embodiments. At block 1302, the method 1300 includes coupling a three-wave mixing device (e.g., the non-degenerate parametric device 102) to a magnetic source (e.g., the magnetic source 182), where the three-wave mixing device is configured to receive a time-varying magnetic flux from the magnetic source (e.g., via port 180). At block 1304, the method 1300 includes configuring the three-wave mixing device (e.g., the non-degenerate parametric device 102) to generate an output signal (e.g., via port 160) having a waveform profile set by the time-varying magnetic flux.

[0062] The time-varying magnetic flux is a time-varying signal having a magnitude that is modulated as a function of time. The three-wave mixing device includes a ring modulator. The waveform profile of the output signal is generated based at least in part on the ring modulator of the three-wave mixing device configured to respond to the time-varying magnetic flux. The three-wave mixing device includes a resonator (e.g., resonator 110 (or resonator a) or resonator 112 (or resonator b)) coupled to the ring modulator. The three-wave mixing device is configured to convert an input signal having an original waveform profile into an output signal having a waveform profile.

[0063] 14 is a flow chart of a method 1400 of configuring the circuit 400, according to one or more embodiments. At block 1402, the method 1400 includes coupling a first three-wave mixing device (e.g., non-degenerate parametric device 102_1) and a second three-wave mixing device (e.g., non-degenerate parametric device 102_2) in the circuit 400, where the first three-wave mixing device is coupled to a first magnetic source (e.g., magnetic source 182_1) to receive a fixed magnetic flux and the second three-wave mixing device is coupled to a second magnetic source (e.g., magnetic source 182_2) to receive a time-varying magnetic flux. At block 1404, the method 1400 includes configuring the circuit 400 to generate (e.g., via port 150_2) an output signal having a waveform profile set by the time-varying magnetic flux.

[0064] A time-varying magnetic flux is a time-varying signal having a magnitude that is modulated as a function of time. A fixed magnetic flux includes a magnitude that remains constant over time. The first three-wave mixing device is configured to provide an intermediate signal (e.g., a converted signal via port 160_1) to a second three-wave mixing device using a first signal (e.g., an input signal via port 150_1) and a second signal (e.g., a pump signal via port 170_1). The second three-wave mixing device is configured to receive the intermediate signal from the first three-wave mixing device (e.g., via port 160_2), and the second three-wave mixing device is configured to use the intermediate signal as an input to generate an output signal (e.g., via port 150_2).

[0065] According to one or more embodiments, the system includes a circuit 400 including a first portion and a second portion, a first magnetic source 182_1 coupled to the first portion and configured to provide a fixed magnetic flux to the first portion, a second magnetic source 182_2 coupled to the second portion and configured to provide a time-varying magnetic flux to the second portion, and the circuit 400 configured to generate an output signal having a waveform profile set by the time-varying magnetic flux.

[0066] The first portion includes a first three-wave mixing device (e.g., non-degenerate parametric device 102_1) and the second portion includes a second three-wave mixing device (e.g., non-degenerate parametric device 102_2). The first portion includes a ring modulator (e.g., Josephson ring modulator 104) configured to interact with a fixed magnetic flux and the second portion includes another ring modulator (e.g., Josephson ring modulator 104) configured to interact with a time-varying magnetic flux. The first portion is configured to output an intermediate signal to the second portion and the second portion is configured to use the intermediate signal as an input to generate an output signal.

[0067] Various embodiments of the present invention are described herein with reference to the associated drawings. Alternative embodiments may be devised without departing from the scope of the present invention. Although various connections and relationships (e.g., above, below, adjacent, etc.) are described between elements in the following description and drawings, those skilled in the art will recognize that many of the relationships described herein are orientation independent, as the described functionality is maintained even when the orientation is changed. These connections and / or relationships may be direct or indirect, unless otherwise specified, and the present invention is not intended to be limited in this respect. Thus, coupling of entities may refer to either direct coupling or indirect coupling, and the relationship between entities may be a direct or indirect relationship. As an example of an indirect relationship, reference in this description to forming layer "A" on layer "B" includes the situation where one or more intermediate layers (e.g., layer "C") are between layers "A" and "B," so long as the associated properties and functionality of layers "A" and "B" are not substantially altered by the intermediate layers.

[0068] The following definitions and abbreviations shall be used for interpreting the claims and the specification. As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having," "contains," or "containing," or any other variation thereof, are intended to include a non-exclusive inclusion. For example, a composition, mixture, process, method, article, or device that includes a list of elements is not necessarily limited to only those elements and may include other elements not expressly listed or inherent to such composition, mixture, process, method, article, or device.

[0069] Moreover, the term "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments or designs. The terms "at least one" and "one or more" are understood to include any integer number greater than or equal to one, i.e., 1, 2, 3, 4, etc. The term "multiple" is understood to include any integer number greater than or equal to two, i.e., 2, 3, 4, 5, etc. The term "connected" can include indirect and direct "connected."

[0070] References in the specification to "one embodiment," "embodiment," "exemplary embodiment," and the like indicate that the embodiment being described may include a particular feature, structure, or characteristic, but that not all embodiments may include that particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Moreover, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is believed to be within the knowledge of one of ordinary skill in the art that it affects such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described.

[0071] For purposes of the following description, the terms "above," "below," "right," "left," "vertical," "horizontal," "upper," "lower," and their derivatives shall refer to the described structures and methods as oriented in the depicted drawings. The terms "overlying," "atop," "on top of," "disposed on," or "disposed on" mean that a first element, such as a first structure, is on a second element, such as a second structure, and that an intervening element, such as an interface structure, may be between the first and second elements. The term "direct contact" means that a first element, such as a first structure, and a second element, such as a second structure, are connected without any intermediate conductive, insulating, or semiconducting layers at the interface of the two elements.

[0072] The terms "about," "substantially," "approximately," and variations thereof are intended to include the degree of error associated with measurement of a particular quantity based on equipment available at the time of the filing of this application. For example, "about" can include a range of ±8%, or 5%, or 2% of a given value.

[0073] The flow charts and block diagrams in the figures illustrate possible implementations of methods of fabrication and / or operation according to various embodiments of the present invention. Various functions / acts of the methods are represented by blocks in the flow diagrams. In some alternative implementations, the functions noted in the blocks may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently or the blocks may sometimes be executed in the reverse order depending upon the functionality involved.

[0074] The description of various embodiments of the present invention is presented for illustrative purposes, but is not intended to be exhaustive or limited to the described embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terms used in this specification have been selected to best explain the principles of the embodiments, practical applications, or technical improvements beyond those found in the market, or to enable other skilled in the art to understand the embodiments described herein.

Claims

1. 1. A method comprising: receiving, by a mixing device, an input signal via a plurality of input ports and a time-varying magnetic flux, the magnetic flux varying over time; generating, by the mixing device, an output signal on an output port using the input signal and the time-varying magnetic flux, the output signal being a signal obtained by frequency conversion from the input signal and having a waveform profile shaped by the time-varying magnetic flux; A method comprising:

2. The method comprises: receiving, by said mixing device, a pump signal at a microwave frequency; 2. The method of claim 1, further comprising: wherein the input signal comprises a signal at a microwave frequency different from the pump signal.

3. The method of claim 1 or 2, wherein the time-varying magnetic flux is a pulsed signal having a magnitude modulated as a function of time.

4. 4. The method of claim 1, wherein the input signal is a continuous wave signal having a fixed amplitude, frequency and phase with respect to time.

5. 5. The method of claim 1, wherein the mixing device is a non-degenerate mixing device and comprises a Josephson ring modulator.

6. 6. The method of claim 1, wherein the waveform profile of the output signal is generated at least in part based on a Josephson ring modulator of the mixing device in response to the time-varying magnetic flux.

7. 1. A method comprising: receiving, by a circuit, an input signal and a time-varying magnetic flux via a plurality of input ports, the circuit including a first mixing device to which the input signal is input and a second mixing device coupled to the first mixing device; generating, by said circuit, an output signal on an output port connected to said second mixing device using said input signal and said time-varying magnetic flux, said output signal being a signal obtained by frequency conversion from said input signal and having a waveform profile shaped by said time-varying magnetic flux; A method comprising:

8. The method of claim 7 , wherein the time-varying magnetic flux is a pulsed signal having a magnitude modulated as a function of time.

9. 9. The method of claim 7 or 8, wherein one of the first mixing device and the second mixing device receives the time-varying magnetic flux and another of the first mixing device and the second mixing device receives a fixed magnetic flux.

10. 10. The method according to claim 7, wherein the first mixing device is configured to provide an intermediate microwave signal to the second mixing device by a first frequency conversion using the microwave signal of the input signal and the microwave signal of a pump signal.

11. 11. The method according to claim 7, wherein the second mixing device is configured to receive an intermediate signal from the first mixing device, and the second mixing device is configured to generate the output signal using the intermediate signal as an input by a second frequency conversion.

12. 1. A method of configuring a circuit, comprising the steps of: coupling a mixing device to a magnetic source, the mixing device being configured to receive a time-varying magnetic flux from the magnetic source via a first input port, the magnetic flux varying over time; configuring the mixing device to receive an input signal via a second input port and to generate an output signal on an output port, the output signal being a signal obtained by frequency conversion from the input signal and having a waveform profile shaped by the time-varying magnetic flux; A method comprising:

13. The method of claim 12 , wherein the time-varying magnetic flux is a pulsed signal having a magnitude modulated as a function of time.

14. 14. The method of claim 12 or 13, wherein the waveform profile of the output signal is generated based at least in part on a Josephson ring modulator of the mixing device configured to respond to the time-varying magnetic flux.

15. 15. The method of claim 12, wherein the mixing device comprises a Josephson ring modulator coupled to a resonator.

16. 16. A method according to any one of claims 12 to 15, wherein the mixing device is configured to convert a continuous input microwave signal into a pulsed output microwave signal having a selected waveform profile.

17. 1. A method of configuring a circuit, comprising the steps of: coupling a first mixing device and a second mixing device in the circuit, the first mixing device being coupled to a first magnetic source to receive a fixed magnetic flux via a first input port and configured to receive an input signal via a second input port, and the second mixing device being coupled to a second magnetic source to receive a time-varying magnetic flux, the magnetic flux varying over time, via a third input port; configuring the circuit to generate an output signal on an output port, the output signal being a signal obtained by frequency conversion from the input signal and having a waveform profile shaped by the time varying magnetic flux; A method comprising:

18. 20. The method of claim 17, wherein the time-varying magnetic flux is a pulsed signal having a magnitude modulated as a function of time.

19. 19. The method of claim 17 or 18, wherein the fixed magnetic flux comprises a magnitude that remains constant over time.

20. 20. The method of claim 17, wherein the first mixing device is configured to provide an intermediate signal to the second mixing device by a first frequency conversion using the input signal and a pump signal.

21. 21. The method of claim 17, wherein the second mixing device is configured to receive an intermediate signal from the first mixing device, and the second mixing device is configured to generate the output signal using the intermediate signal as an input by a second frequency conversion.

22. 1. A system comprising: The circuit, a first magnetic source coupled to a first portion of the circuit and configured to provide a fixed magnetic flux to the first portion via a first input port; a second magnetic source coupled to a second portion of the circuit and configured to provide a time-varying magnetic flux to the second portion via a second input port, the magnetic flux varying over time; the second magnetic source, the circuit configured to receive an input signal via a third input port and generate an output signal on an output port, the output signal being a signal obtained by frequency conversion from the input signal and having a waveform profile shaped by the time-varying magnetic flux; A system comprising:

23. 23. The system of claim 22, wherein the first portion includes a first mixing device and the second portion includes a second mixing device, the first mixing device and the second mixing device being non-degenerate mixing devices.

24. 24. The system of claim 22 or 23, wherein the first portion includes a Josephson ring modulator configured to interact with the fixed magnetic flux and the second portion includes another Josephson ring modulator configured to interact with the time-varying magnetic flux.

25. the first part is configured to output an intermediate signal to the second part through a first frequency conversion; 25. A system according to any one of claims 22 to 24, wherein the second part is configured to generate the output signal using the intermediate signal as an input by a second frequency conversion.

Images