Flying microwave qubits with nearly perfect transfer efficiency

TL;DR

This paper presents a nearly perfect method for transferring microwave qubit states between resonators using tunable couplers, achieving efficiencies close to 100% with practical superconducting technology.

Contribution

It introduces a novel protocol for high-efficiency microwave qubit transfer employing tunable couplers with time-varying transmission coefficients.

Findings

Achieves theoretical transfer efficiency of 99.9%.

Transfer duration is approximately 400 ns with current superconducting technology.

Method can be adapted for optical photon quantum state transfer.

Abstract

We propose a procedure for transferring the state a microwave qubit via a transmission line from one resonator to another resonator, with a theoretical efficiency arbitrarily close to 100%. The emission and capture of the microwave energy is performed using tunable couplers, whose transmission coefficients vary in time. Using the superconducting phase qubit technology and tunable couplers with maximum coupling of 100 MHz, the procedure with theoretical efficiency $\eta=0.999$ requires a duration of about 400 ns (excluding propagation time) and an ON/OFF ratio of 45. The procedure may also be used for a quantum state transfer with optical photons.