Controlled catch and release of microwave photon states

TL;DR

This paper demonstrates a superconducting system that can switch between long photon storage and strong measurement modes by controlling coupling, enabling precise photon waveform shaping for quantum information applications.

Contribution

It introduces a variable coupling superconducting resonator-qubit system that allows dynamic control of photon emission rates and waveform shaping, advancing quantum state transfer techniques.

Findings

Achieved adjustable photon emission rate up to 1,000 times the intrinsic decay

Controlled release of coherent and non-classical Fock states

Shaped photon waveforms dynamically for quantum communication

Abstract

The quantum behavior of superconducting qubits coupled to resonators is very similar to that of atoms in optical cavities [1, 2], in which the resonant cavity confines photons and promotes strong light-matter interactions. The cavity end-mirrors determine the performance of the coupled system, with higher mirror reflectivity yielding better quantum coherence, but higher mirror transparency giving improved measurement and control, forcing a compromise. An alternative is to control the mirror transparency, enabling switching between long photon lifetime during quantum interactions and large signal strength when performing measurements. Here we demonstrate the superconducting analogue, using a quantum system comprising a resonator and a qubit, with variable coupling to a measurement transmission line. The coupling can be adjusted through zero to a photon emission rate 1,000 times the intrinsic photon decay rate. We use this system to control photons in coherent states as well as in non-classical Fock states, and dynamically shape the waveform of released photons. This has direct applications to circuit quantum electrodynamics [3], and may enable high-fidelity quantum state transfer between distant qubits, for which precisely-controlled waveform shaping is a critical and non-trivial requirement [4, 5].