Parametric amplifiers with inductive input coupling for quantum computing systems
The disclosure is towards parametric amplifiers with inductive input coupling for quantum computing systems. One example aspect of the present disclosure is directed to a quantum computing system comprising a first qubit, a first measurement device, and a first amplifier. The first measurement device is configured to generate a first qubit signal corresponding to a first quantum state of the first qubit. The first amplifier is configured to amplify the first qubit signal. The first amplifier comprises a first transmission-line resonator. The first transmission-line resonator provides an inductive reactance for an electrical coupling between the first measurement device and the first amplifier. The inductive reactance for the electrical coupling enables a transmission of the first qubit signal.
1 . A quantum computing system comprising:
a first qubit;
a first measurement device configured to generate a first qubit signal corresponding to a first quantum state of the first qubit; and
a first amplifier configured to amplify the first qubit signal, wherein the first amplifier comprises a first transmission-line resonator that inverts an input coupling reactance of the first amplifier from a capacitive reactance to an inductive reactance, which provides an electrical coupling between the first measurement device and the first amplifier, and the inductive reactance for the electrical coupling enables a transmission of the first qubit signal.
2 . The quantum computing system of claim 1 , wherein the first amplifier is a Josephson parametric amplifier.
3 . The quantum computing system of claim 1 , wherein the first amplifier further comprises a multi-polar impedance matching network that includes a first pole, a second pole, and a third pole.
4 . The quantum computing system of claim 3 , wherein the third pole includes the first transmission-line resonator.
5 . The quantum computing system of claim 4 , wherein a terminal transmission line of the third pole includes a shunt inductor.
6 . The quantum computing system of claim 3 , wherein the first pole includes a first inductive-capacitive (LC) resonating circuit and the second pole includes a second LC resonating circuit.
7 . The quantum computing system of claim 6 , wherein a first capacitor electrically couples the first transmission-line resonator to the second LC resonating circuit.
8 . The quantum computing system of claim 7 , wherein a second capacitor electrically couples the first LC-resonating circuit to the second LC resonating circuit.
9 . The quantum computing system of claim 1 , wherein a non-linear inductor of the first amplifier includes at least one of Josephson Junction, a direct current (DC) superconducting quantum interference device (SQUID), or a radiofrequency (RF) SQUID.
10 . The quantum computing system of claim 1 , wherein the first transmission-line resonator electrically couples a terminal line of the first amplifier to one or more poles of an impedance match network of the first amplifier.
11 . The quantum computing system of claim 1 , wherein the first amplifier has a gain of within a range of 15-25 decibels (dBs).
12 . The quantum computing system of claim 1 , wherein a bandwidth of the first amplifier has a mean frequency of within a range of 4-10 GHz.
13 . The quantum computing system of claim 1 , wherein a bandwidth of the first amplifier has a full-width half-max (FWHM) within a range of 200-600 MHz.
14 . An amplifier device comprising:
a first pole that includes a first inductive-capacitive (LC) resonating circuit;
a second pole that includes a transmission-line resonator that provides an inductive reactance for an input to the amplifier device;
a third pole that includes a second LC resonating circuit; and
a capacitor that electrically couples the first pole and the third pole.
15 . The amplifier device of claim 14 , further comprising:
a multi-polar impedance matching network that includes the first pole, the second pole, and the third pole.
16 . The amplifier device of claim 14 , wherein the second pole further includes a shunt inductor.
17 . The amplifier device of claim 14 , wherein a first inductor of the first LC resonating circuit has a variable inductance.
18 . A quantum computing system comprising:
a set of qubits;
a set of transmission lines, wherein each transmission line of the set of transmission lines is configured to transmit a qubit signal that encodes a measurement of a quantum state of a corresponding qubit of the set of qubits; and
a set of Josephson parametric amplifiers (JPAs), wherein each JPA of the set of JPAs includes a quarter-wavelength transmission-line resonator that electrically couples, via an inductive reactance, the respective JPA to a corresponding transmission line of the set of transmission lines such that the corresponding transmission line inductively provides its qubit signal to the respective JPA for amplification.
19 . The quantum computing system of claim 18 , wherein the quarter-wavelength transmission-line resonator of the respective JPA is configured to invert an input coupling reactance of the respective JPA from a capacitive reactance to the inductive reactance.
20 . The quantum computing system of claim 1 , wherein the first transmission-line resonator is a quarter-wavelength resonator.