Topological quantum state control through exceptional-point proximity

TL;DR

This paper demonstrates a novel method for controlling quantum states using non-Hermitian dynamics near exceptional points in a superconducting circuit, enabling non-reciprocal state transfer and chiral phase manipulation.

Contribution

It introduces a new approach to quantum control by exploiting exceptional points in a dissipative superconducting qubit, revealing non-reciprocal and chiral effects in quantum evolution.

Findings

Real-time tuning around exceptional points causes non-reciprocal quantum state transfer.

Observation of chiral geometric phases confirms quantum coherence during state transport.

Demonstrates a new method for quantum bath engineering via non-Hermitian control.

Abstract

We study the quantum evolution of a non-Hermitian qubit realized as a submanifold of a dissipative superconducting transmon circuit. Real-time tuning of the system parameters to encircle an exceptional point results in non-reciprocal quantum state transfer. We further observe chiral geometric phases accumulated under state transport, verifying the quantum coherent nature of the evolution in the complex energy landscape and distinguishing between coherent and incoherent effects associated with exceptional point encircling. Our work demonstrates an entirely new method for control over quantum state vectors, highlighting new facets of quantum bath engineering enabled through dynamical non-Hermitian control.