Systems and methods for superconducting flux qubit readout

摘要

Systems and methods for reading out the states of superconducting flux qubits may couple magnetic flux representative of a qubit state to a DC-SQUID in a variable transformer circuit. The DC-SQUID is electrically coupled in parallel with a primary inductor such that a time-varying (e.g., AC) drive current is divided between the DC-SQUID and the primary inductor in a ratio that is dependent on the qubit state. The primary inductor is inductively coupled to a secondary inductor to provide a time-varying (e.g., AC) output signal indicative of the qubit state without causing the DC-SQUID to switch into a voltage state. Coupling between the superconducting flux qubit and the DC-SQUID may be mediated by a routing system including a plurality of latching qubits. Multiple superconducting flux qubits may be coupled to the same routing system so that a single variable transformer circuit may be used to measure the states of multiple qubits.

主权项

1. A superconducting readout system comprising:
a first superconducting flux qubit including a qubit loop formed of a material that is superconducting below a critical temperature and at least one Josephson junction; a signal input line; a signal output line; and a variable transformer circuit comprising a DC-SQUID, a primary inductor, and a secondary inductor, wherein the DC-SQUID is communicatively coupleable to the qubit loop of the first superconducting flux qubit, the DC-SQUID and the primary inductor are electrically connected in parallel with one another with respect to the signal input line, the primary inductor and the secondary inductor are positioned sufficiently proximate one another to inductively couple signals therebetween, and the secondary inductor is electrically connected in series with the signal output line.