Coupling device design method, superconducting quantum circuit and system

Abstract

The invention discloses a design method of a quantum bit-readout cavity coupling device, a superconducting quantum circuit and a superconducting quantum system. An interdigital capacitor directly connected with a readout cavity is changed to be directly connected with a cross capacitor of a quantum bit. By means of the design, quantum bit circuit parameters determined through calculation and readout cavity circuit parameters determined through simulation in an existing scheme can be improved into the mode that the quantum bit circuit parameters are determined through simulation and calculation, and the readout cavity circuit parameters are determined through calculation; therefore, the method has the following beneficial effects: 1) the influence of the original interdigital capacitor on the readout cavity is transferred to the cross capacitor of the quantum bit, so that the frequency detuning of the quantum bit-readout cavity is increased, and the readout design requirement is easy to meet; and 2) parameters determined through simulation are changed into quantum bit circuit parameters from readout cavity circuit parameters, so that the memory and time overhead occupied by modeling simulation during superconducting quantum circuit design can be reduced, and the design period is shortened.

Description

technical field [0001] The invention relates to the field of superconducting quantum, in particular to a design method of a quantum bit-reading cavity coupling device, a superconducting quantum circuit and a system. Background technique [0002] Superconducting quantum circuits include quantum bits, readout cavities, and interdigitated capacitors. Among them, the quantum bit is a macro resonance circuit composed of a SQUID (Superconducting quantum interference device, superconducting quantum interference device) and a bypass capacitor in parallel. For transmon (transmission-line shunted plasma oscillation qubit, bypass parallel plasma oscillation qubit) qubit, the bypass capacitor usually chooses a cross capacitor. The readout cavity is used to read out the state of the qubit. From a structural point of view, the readout cavity is a quarter-wavelength CPW (Coplanar waveguide, coplanar waveguide) resonator, and the occupied area is reduced by meandering arrangement. like f...

AI Technical Summary

Problems solved by technology

[0004] However, in the existing scheme, the interdigital capacitor is connected to the readout cavity as a qubit-readout cavity coupling device, and there will be the following problems in the design of superconducting quantum circuits: 1) the geometric size of the interdigital capacitor itself cannot be ignored, It will increase the reflection surface of the microwave transmission in the readout cavity, resulting in phase shift, causing the intrinsic frequency of the readout cavity to shift to a low frequency. As a result, the qubit-readout cavity frequency mismatch will be reduced, which cannot meet the readout design Require

2) The interdigital capacitor is connected to the readout cavity, and the circuit parameters of the readout cavity will be affected by the interdigital capacitor. Due to the special shape of the interdigital capacitor, the circuit parameters (eigenfrequency and self-capacitance) of the readout cavity cannot be summarized. The general calculation formula, that is, the circuit parameters of the readout cavity cannot be obtained through simple calculations, but can only be obtained through simulation, but the simulation requires the interdigital capacitors to be modeled together with the readout cavity, and the readout cavity has been twisted to reduce the occupied area. Arrangement, the model is still very large when performing simulation analysis, which will obviously increase memory and time overhead, thereby increasing the design cycle

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