Josephson parametric amplifier, quantum computing device and quantum computing system

Abstract

The embodiment of the invention provides a Josephson parametric amplifier which is applied to the field of quantum computing. The Josephson parametric amplifier includes a first port, a nonlinear resonator, a ground circuit, a coupling capacitor, and a pump circuit. The pump circuit is used for receiving a pump signal, and energy is provided for the nonlinear resonator through the pump signal. The nonlinear resonator receives a first signal through the first port and amplifies the first signal to obtain a second signal. The nonlinear resonator is also configured to output a second signal through the first port. A coupling capacitor is arranged between the nonlinear resonator and the first port. A first connection point is arranged between the first port and the coupling capacitor. One end of the grounding circuit is connected with the first connection point. The other end of the grounding circuit is grounded. The resonant frequency of the ground circuit is greater than the operating frequency of the nonlinear resonator. In the technical scheme provided by the invention, the Josephson parametric amplifier is used for amplifying the signal, so that the signal-to-noise ratio of signal reading can be improved.

Description

Technical Field

[0001] The present application relates to the field of quantum computing, and in particular to a Josephson parametric amplifier, a quantum computing device and a system. Background Art

[0002] Quantum computing devices work in ultra-low temperature environments and are composed of basic components such as capacitors, inductors, transmission lines, and Josephson junctions. The Josephson junction provides the basic structure of superconducting quantum bits. When performing quantum computing, the quantum computing device needs to input a microwave reading signal. The microwave reading signal interacts with the superconducting quantum bit to complete the calculation process and obtain a microwave output signal. The quantum reading device reads the result of each quantum bit calculation at room temperature through the microwave output signal. However, the power of the microwave output signal is low. The thermal noise introduced by the room temperature environment is much higher than the power of the microwave output signal, resulting in a low signal-to-noise ratio for the signal reading. Summary of the invention

[0003] The present application provides a Josephson parametric amplifier, a quantum computing device and a system, which can improve the signal-to-noise ratio of signal reading by amplifying the signal through the Josephson parametric amplifier.

[0004] In a first aspect, the present application provides a Josephson parametric amplifier. The Josephson parametric amplifier includes a first port, a nonlinear resonator, a grounding circuit, a coupling capacitor and a pumping circuit. The pumping circuit is coupled to the nonlinear resonator. The pumping circuit is used to receive a pumping signal and provide energy to the nonlinear resonator through the pumping signal. The nonlinear resonator receives a first signal through the first port, amplifies the first signal, and obtains a second signal. The first signal can also be referred to as a signal to be amplified. The second signal can also be referred to as an amplified signal. The nonlinear resonator is also used to output a second signal through the first port. A coupling capacitor is provided between the nonlinear resonator and the first port. A first connection point is provided between the first port and the coupling capacitor. One end of the grounding circuit is connected to the first connection point. The other end of the grounding circuit is grounded. The resonant frequency of the grounding circuit is greater than the operating frequency of the nonlinear resonator.

[0005] In an optional manner of the first aspect, the grounding circuit includes a first inductor and a first capacitor connected in parallel. By using the inductor and the capacitor as the grounding circuit, the size of the grounding circuit can be reduced, thereby reducing the size of the Josephson parametric amplifier.

[0006] In an optional manner of the first aspect, the first inductance is greater than 1 picohenry (pH), and the first capacitance is greater than 1 femtofarad (fF).

[0007] In an optional manner of the first aspect, the grounding circuit is a transmission line. By using the transmission line as the grounding circuit, the loss of the grounding circuit can be reduced.

[0008] In an optional manner of the first aspect, the length of the transmission line is between 0 and 300 mm.

[0009] In an optional manner of the first aspect, the coupling capacitor has a size between 10 fF and 100 pF.

[0010] In an optional manner of the first aspect, the nonlinear resonator includes a grounded capacitor and a DC superconducting quantum interference device connected in parallel, the grounded capacitor has a size between 10 fF and 100 pF, and the DC superconducting quantum interference device has an inductance between 10 pH and 100 nH in the absence of an external magnetic field.

[0011] In an optional manner of the first aspect, the grounding circuit includes a plurality of resonant frequencies, and the plurality of resonant frequencies are all greater than an operating frequency of the Josephson parametric amplifier.

[0012] In an optional form of the first aspect, the bandwidth of the Josephson parametric amplifier is greater than 100 megahertz (MHz).

[0013] In an optional manner of the first aspect, a bandwidth of the Josephson parametric amplifier is greater than 600 MHz.

[0014] In an optional manner of the first aspect, the pump signal includes a direct current signal and a radio frequency signal. The direct current signal is used to set the operating frequency of the nonlinear resonator. The radio frequency signal is used to provide energy for the nonlinear resonator.

[0015] The second aspect of the present application provides a quantum computing device. The quantum computing device includes a quantum chip, a circulator, and the Josephson parametric amplifier described in the first aspect or any optional method of the first aspect. The quantum chip is used to transmit a first signal to the Josephson parametric amplifier through the circulator. The Josephson parametric amplifier is used to amplify the first signal to obtain a second signal, and output the second signal through the circulator.

[0016] The third aspect of the present application provides a quantum computing system. The quantum computing system includes a reading device and the quantum computing device described in the second aspect. The reading device is used to generate a reading signal and a pumping signal, and transmit the reading signal and the pumping signal to the quantum computing device. The quantum computing device is used to output a second signal according to the reading signal and the pumping signal. The reading device is used to obtain the second signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A first structural schematic diagram of a Josephson parametric amplifier provided in an embodiment of the present application;

[0018] Figure 2 A second structural schematic diagram of a Josephson parametric amplifier provided in an embodiment of the present application;

[0019] Figure 3 A third structural schematic diagram of a Josephson parametric amplifier provided in an embodiment of the present application;

[0020] Figure 4 A fourth structural schematic diagram of a Josephson parametric amplifier provided in an embodiment of the present application;

[0021] Figure 5 A fifth schematic diagram of a Josephson parametric amplifier provided in an embodiment of the present application;

[0022] Figure 6 A first structural schematic diagram of a quantum computing device provided in an embodiment of the present application;

[0023] Figure 7 A second structural schematic diagram of a quantum computing device provided in an embodiment of the present application;

[0024] Figure 8 A first structural schematic diagram of a quantum computing system provided in an embodiment of the present application;

[0025] Fig. 9 A second schematic diagram of the structure of a quantum computing system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0026] The present application provides a Josephson parametric amplifier, a quantum computing device and a system, which can improve the signal-to-noise ratio of signal reading by amplifying the signal through the Josephson parametric amplifier. It should be understood that the "first", "second", etc. used in the present application are only used for the purpose of distinguishing the description, and cannot be understood as indicating or implying relative importance, nor can they be understood as indicating or implying order. In addition, for the sake of simplicity and clarity, reference numbers and / or letters are repeated in multiple figures of the present application. Repetition does not indicate a strict limiting relationship between various embodiments and / or configurations. For the convenience of explanation, some professional terms appearing in the embodiments of the present application are explained below.

[0027] Quantum bit: The most basic unit of quantum information processing, with two intrinsic energy states. Compared with the bits of classical computers, which have two states of 0 and 1, quantum bits can also be in a superposition state of 0 and 1.

[0028] Josephson junction: A sandwich-structured device consisting of a superconducting metal layer, an insulating layer, and a superconducting metal layer. It is used as a nonlinear inductor and is the core device of superconducting quantum computing.

[0029] DC superconducting quantum interference device (SQUID): A loop device formed by two Josephson junctions in parallel, generally used as an adjustable inductor. The inductance of a DC superconducting quantum interference device can be changed by changing the magnetic flux in the loop device.

[0030] Josephson parametric amplifier: A quantum limit amplifier that includes a nonlinear resonator formed by connecting a capacitor in parallel with a DC superconducting quantum interference device, and that amplifies using the nonlinear or parametric adjustable principle of the nonlinear resonator and operates at the quantum bit operating temperature.

[0031] The external environment of the amplifier: The parts other than the Josephson parametric amplifier that are connected to the Josephson parametric amplifier through input and output lines are collectively referred to as the external environment of the amplifier.

[0032] The Josephson parametric amplifier provided in this application is applied to the field of quantum computing. In the field of quantum computing, quantum computing can be performed in an ultra-low temperature environment by a quantum computing device to obtain a microwave output signal. However, the quantum reading device needs to read the microwave output signal at room temperature. The thermal noise introduced by the room temperature environment is much higher than the power of the microwave output signal, resulting in a low signal-to-noise ratio for signal reading.

[0033] To this end, the present application provides a Josephson parametric amplifier. Figure 1 The first structural diagram of the Josephson parametric amplifier provided in the embodiment of the present application is shown in FIG. Figure 1As shown, the Josephson parametric amplifier 100 includes a port 1, a port 2, a grounding circuit 101, a coupling capacitor 102, a nonlinear resonator 103 and a pumping circuit 104. Port 2 can also be called a second port. One end of the pumping circuit 104 is connected to port 2, and the other end is grounded. The pumping circuit 104 receives a pumping signal through port 2. The pumping circuit 104 is coupled to the nonlinear resonator 103. For example, the pumping circuit 104 and the nonlinear resonator 103 are coupled by mutual inductance. The pumping circuit 104 provides energy to the nonlinear resonator 103 through the pumping signal. One end of the nonlinear resonator 103 is connected to port 1, and the other end is grounded. The nonlinear resonator 103 receives a first signal through port 1. Port 1 can also be called a first port. The first signal can also be called a signal to be amplified. The first signal is a microwave output signal of a quantum chip. The nonlinear resonator 103 refers to a nonlinear resonator formed by connecting a capacitor and a DC superconducting quantum interference device in parallel. The nonlinear resonator 103 amplifies the first signal according to the pumping signal to obtain a second signal. The second signal can also be called an amplified signal. The nonlinear resonator 103 outputs the second signal through port 1. A coupling capacitor 102 is arranged between port 1 and the nonlinear resonator 103. A first connection point 105 is arranged between port 1 and the coupling capacitor 102. One end of the grounding circuit 101 is connected to the first connection point 105. The other end of the grounding circuit 101 is grounded. The grounding circuit 101 can have one or more resonance modes, and the resonance frequency of each resonance mode is different. The resonance frequency of each resonance mode can be determined by the point where the imaginary part of the admittance of the grounding circuit 101 is equal to 0. At least one resonance frequency of the grounding circuit 101 is greater than the operating frequency of the nonlinear resonator 103. Among them, the imaginary part of the admittance of the grounding circuit 101 p=Im(Y(ω)). Among them, Y(ω) represents the grounding circuit 101.

[0034] In the embodiment of the present application, the first signal is amplified by the Josephson parametric amplifier 100, so that the signal-to-noise ratio of the signal reading can be improved. In addition, the nonlinear resonator 103 is connected to the external environment through the coupling capacitor 102, and the grounding circuit 101 is also coupled to the nonlinear resonator 103 through the coupling capacitor 102. The grounding circuit 101 can change the circuit response of the nonlinear resonator 103 near the operating frequency without affecting the operating frequency of the nonlinear resonator 103, thereby improving the operating bandwidth of the Josephson parametric amplifier 100. For example, in the embodiment of the present application, the operating bandwidth of the Josephson parametric amplifier 100 can be greater than 100MHz or 600MHz.

[0035] Figure 2 The second structural diagram of the Josephson parametric amplifier provided in the embodiment of the present application is shown in FIG. Figure 2 As shown, in Figure 1On the basis of, the grounding circuit 101 includes a first inductor 201 and a first capacitor 202 connected in parallel. One end of the first inductor 201 and the first capacitor 202 is connected to the first connection point 105, and the other end is grounded. The inductance of the first inductor 201 can be greater than 1 picohenry. The capacitance of the first capacitor 202 can be greater than 1 fF. The pumping circuit 104 includes a pumping signal line 203. The pumping signal line 203 is coupled to the nonlinear resonator 103.

[0036] Figure 3 The third structural diagram of the Josephson parametric amplifier provided in the embodiment of the present application is shown in FIG. Figure 3 As shown, in Figure 2 On the basis of, the nonlinear resonator 103 includes a grounded capacitor 301 and a DC superconducting quantum interference device 302 in parallel. One end of the grounded capacitor 301 and the DC superconducting quantum interference device 302 is connected to the coupling capacitor 102, and the other end is grounded. The capacitance of the grounded capacitor 301 can be between 10fF and 100 pF. The pump signal line 203 is coupled to the DC superconducting quantum interference device 302 in the nonlinear resonator 103. In practical applications, the nonlinear resonator 103 can also include a second inductor. The second inductor is connected in series with the DC superconducting quantum interference device 302 and in parallel with the grounded capacitor 301.

[0037] Figure 4 The fourth structural diagram of the Josephson parametric amplifier provided in the embodiment of the present application. Figure 4 As shown, in Figure 1 On the basis of, the grounding circuit 101 includes a transmission line 401. The transmission line 401 can be a coplanar waveguide, a microstrip line or a stripline. One end of the transmission line 401 is connected to the first connection point 105, and the other end is grounded. The length of the transmission line 401 can be between 0 and 300 mm. The nonlinear resonator 103 includes a parallel grounding capacitor 301 and a DC superconducting quantum interference device 302. The pumping circuit 104 includes a pumping signal line 203. The pumping signal line 203 is coupled to the DC superconducting quantum interference device 302.

[0038] It should be understood that the aforementioned Figures 1 to 4 These are just a few examples of the Josephson parametric amplifier 100 provided in the embodiments of the present application. In practical applications, those skilled in the art can adaptively modify the structure of the Josephson parametric amplifier 100 according to requirements. For example, the Josephson parametric amplifier 100 includes a plurality of DC superconducting quantum interference devices 302 connected in series. Figure 5 This is the fifth schematic diagram of the Josephson parametric amplifier provided in the embodiment of the present application. Figure 5 As shown, in Figure 3 On the basis of, the nonlinear resonator 103 further includes a DC superconducting quantum interference device 501. The DC superconducting quantum interference device 501 and the DC superconducting quantum interference device 302 are connected in series.

[0039] In practical applications, the pump signal can include signals of two frequencies, namely a DC signal and a RF signal. The DC signal is used to set the operating frequency of the nonlinear resonator 103. The RF signal is used to provide energy to the nonlinear resonator 103. The frequency of the RF signal can be the same as the frequency of the first signal, or can be twice the frequency of the first signal. When the frequency of the RF signal is the same as the frequency of the first signal, the nonlinear resonator 103 can also receive the RF signal through port 1.

[0040] The Josephson parametric amplifier provided by the present application is described above, and the quantum computing device and quantum computing system provided by the present application are described below. Figure 6 The first structural diagram of the quantum computing device provided in the embodiment of the present application. Figure 6 As shown, the quantum computing device 600 includes a quantum chip 601, a circulator 602, and a Josephson parametric amplifier 100. The quantum chip 601 is a core component for performing quantum computing, and is used to transmit a first signal to the circulator 602. One port of the circulator 602 is used to receive the first signal, and transmit the first signal to the Josephson parametric amplifier 100 through another port. The Josephson parametric amplifier 100 is used to output a second signal according to the first signal. The description of the Josephson parametric amplifier 100 can refer to the aforementioned Figures 1 to 5 The circulator 602 is also used to receive the second signal through the port outputting the first signal, and output the second signal through another port.

[0041] In practical applications, the first signal may have a reflected signal during transmission. For example, the port of the circulator 602 receiving the first signal may reflect the first signal. The reflected signal may affect the normal operation of the quantum chip 601. In order to reduce the impact of the reflected signal on the quantum chip 601, the quantum computing device 600 can also include one or more isolators. Figure 7 A second schematic diagram of the structure of a quantum computing device provided in an embodiment of the present application is shown in FIG. Figure 7 As shown, in Figure 6 On the basis of, the quantum computing device 600 further includes an isolator 701 and an isolator 702. The isolator 701 is located between the quantum chip 601 and the circulator 602. The isolator 702 is located between the port of the circulator 602 outputting the second signal and the output port of the quantum computing device 600.

[0042] Figure 8 The first schematic diagram of the structure of the quantum computing system provided in the embodiment of the present application. Figure 8As shown, the quantum computing system includes a reading device 800 and a quantum computing device 600. The reading device 800 is used to generate a reading signal and a pumping signal, and transmit the reading signal and the pumping signal to the quantum computing device 600. The quantum chip 601 is used to generate a first signal according to the reading signal, and transmit the first signal to the circulator 602. The operating frequency of the reading signal and the first signal can also be called the operating frequency of the Josephson parametric amplifier 100. One port of the circulator 602 is used to receive the first signal, and transmit the first signal to the Josephson parametric amplifier 100 through another port. The Josephson parametric amplifier 100 is used to amplify the first signal according to the pumping signal to obtain a second signal. The circulator 602 is also used to receive the second signal through the port that outputs the first signal, and output the second signal to the reading device 800 through another port. The reading device 800 is also used to receive the second signal from the quantum computing device 600.

[0043] Fig. 9 This is a second schematic diagram of the structure of the quantum computing system provided in the embodiment of the present application. Fig. 9 As shown, in Figure 8 On the basis of, the reading device 800 includes a signal generator 902, a signal receiver 903 and a pump source 904. Among them, the signal generator 902 is used to generate a read signal. The pump source 904 is used to generate a pump signal. The signal receiver 903 is used to receive a second signal from the reading device 800. The front end of the signal receiver 903 can also be connected to a radio frequency amplifier. The radio frequency amplifier is used to amplify the second signal. The quantum computing device 600 also includes a high electron mobility transistor (HETM) 901. HETM 901 is used to amplify the first signal. In an embodiment of the present application, HETM 901 can operate in an environment with a temperature of about 4 Kelvin. The quantum computing device 600 can operate in an environment with a temperature below 30 milliKelvin. The reading device 800 can operate in a normal room temperature environment.

[0044] The above are only specific implementation methods of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be covered by the protection scope of the present application.

Claims

1. A Josephson parametric amplifier, characterized in that: The invention comprises a first port, a nonlinear resonator, a grounding circuit, a coupling capacitor and a pumping circuit, wherein: The pump circuit is used to receive a pump signal and provide energy to the nonlinear resonator through the pump signal; The nonlinear resonator receives a first signal through the first port, amplifies the first signal to obtain a second signal, and outputs the second signal through the first port; The coupling capacitor is arranged between the nonlinear resonator and the first port; A first connection point is provided between the first port and the coupling capacitor, one end of the grounding circuit is connected to the first connection point, the other end of the grounding circuit is grounded, and the resonant frequency of the grounding circuit is greater than the operating frequency of the nonlinear resonator.

2. The Josephson parametric amplifier according to claim 1, characterized in that: The grounding circuit includes a first inductor and a first capacitor connected in parallel.

3. The Josephson parametric amplifier according to claim 2, characterized in that: The first inductance is greater than 1 picohenry, and the first capacitance is greater than 1 femtofarad.

4. The Josephson parametric amplifier according to claim 1, characterized in that: The grounding circuit is a transmission line.

5. The Josephson parametric amplifier according to claim 4, characterized in that: The length of the transmission line is between 0 and 300 mm.

6. The Josephson parametric amplifier according to any one of claims 1 to 5, characterized in that: The coupling capacitor has a size between 10 femtofarads and 100 picofarads.

7. The Josephson parametric amplifier according to any one of claims 1 to 6, characterized in that: The nonlinear resonator includes a grounding capacitor and a DC superconducting quantum interference device connected in parallel. The grounding capacitor has an inductance between 10 femtofarads and 100 picofarads. The inductance of the DC superconducting quantum interference device when there is no external magnetic field is between 10 picohenry and 100 nanohenry.

8. The Josephson parametric amplifier according to any one of claims 1 to 7, characterized in that: The grounding circuit includes a plurality of resonant frequencies, and the plurality of resonant frequencies are all greater than the operating frequency of the Josephson parametric amplifier.

9. The Josephson parametric amplifier according to any one of claims 1 to 8, characterized in that: The bandwidth of the Josephson parametric amplifier is greater than 100 MHz.

10. The Josephson parametric amplifier according to any one of claims 1 to 9, characterized in that: The pump signal includes a direct current signal and a radio frequency signal. The direct current signal is used to set the operating frequency of the nonlinear resonator, and the radio frequency signal is used to provide energy for the nonlinear resonator.

11. A quantum computing device, characterized in that: The method comprises a quantum chip, a circulator and a Josephson parametric amplifier as claimed in any one of claims 1 to 10, wherein: The quantum chip is used to transmit a first signal to the Josephson parametric amplifier through the circulator; The Josephson parametric amplifier is used to amplify the first signal to obtain a second signal, and output the second signal through the circulator.

12. A quantum computing system, characterized in that: A reading device and a quantum computing device as claimed in claim 11, wherein: The reading device is used to generate a reading signal and a pumping signal, and transmit the reading signal and the pumping signal to the quantum computing device; The quantum computing device is used to output a second signal according to the read signal and the pump signal; The reading device is used to obtain the second signal.

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