Fast readout of a single Cooper-pair box using its quantum capacitance

TL;DR

This paper demonstrates a rapid single-shot readout of a Cooper-pair box using quantum capacitance detection via a resonator, achieving measurement times ten times faster than previous methods.

Contribution

The authors developed an optimized resonator-based readout method utilizing quantum capacitance, enabling significantly faster measurement of a Cooper-pair box state.

Findings

Single shot parity measurement in ~50 ns

Readout speed is an order of magnitude faster than prior techniques

Effective characterization of quasiparticle tunneling events

Abstract

We have fabricated a single Cooper-pair box (SCB) together with an on-chip lumped element resonator. By utilizing the quantum capacitance of the SCB, its state can be read out by detecting the phase of a radio-frequency (rf) signal reflected off the resonator. The resonator was optimized for fast readout. By studying quasiparticle tunneling events in the SCB, we have characterized the performance of the readout and found that we can perform a single shot parity measurement in approximately 50 ns. This is an order of magnitude faster than previously reported measurements.