US 11,940,392 B2
Measurement scheme for superconducting qubits using low-frequency microwave signals within a dilution refrigerator
Baleegh Abdo, Fishkill, NY (US)
Assigned to INTERNATIONAL BUSINESS MACHINES CORPORATION, Armonk, NY (US)
Filed by International Business Machines Corporation, Armonk, NY (US)
Filed on Apr. 18, 2019, as Appl. No. 16/387,789.
Prior Publication US 2020/0333263 A1, Oct. 22, 2020
Int. Cl. G01N 22/00 (2006.01); G06N 10/00 (2022.01)
CPC G01N 22/00 (2013.01) [G06N 10/00 (2019.01)] 13 Claims
OG exemplary drawing
 
1. A system, comprising: a dilution refrigerator for a quantum processor, wherein the dilution refrigerator comprises:
a first Josephson mixer circuit configured to upconvert an input microwave signal comprising a first frequency from a classical computing system via an input transmission line to a qubit readout signal comprising a second frequency in a defined range of a readout resonance frequency for performing a qubit readout to obtain a qubit measurement associated with the quantum processor, wherein the first Josephson mixer circuit comprises a Josephson ring modulator coupled to a lumped-element microwave resonator and a surface acoustic wave resonator, and wherein the lumped-element microwave resonator resonates at a first resonance frequency that is different from a second resonance frequency at which the surface acoustic wave resonator resonates;
a Josephson based circulator coupled to the quantum processor, wherein the Josephson based circulator is configured to:
route the qubit readout signal to the quantum processor, wherein a portion of the qubit readout signal is reflected off of the quantum processor to produce a readout output signal associated with qubit information from the quantum processor, and
route the readout output signal towards a second Josephson mixer circuit; and
the second Josephson mixer circuit is configured to:
convert the readout output signal to a reduced-frequency microwave signal having a third frequency that is lower than the second frequency, and route the reduced-frequency microwave signal towards an output transmission line coupled to the classical computing system;
wherein frequency increases performed by the first Josephson mixer circuit and frequency decreases performed by the second Josephson mixer circuit improve accuracy of the qubit measurement associated with the quantum processor.