Quantum optical circulator controlled by a single chirally coupled atom

Non-Reciprocal Transmission and Reflection of a Chirally-Coupled Quantum Dot

We report strongly non-reciprocal behaviour for quantum dot exciton spins coupled to nano-photonic waveguides under resonant laser excitation. A clear dependence of the transmission spectrum on the propagation direction is found for a chirally-coupled quantum dot, with spin up and spin down exciton spins coupling to the left and right propagation directions respectively. The reflection signal shows an opposite trend to the transmission, which a numerical model indicates is due to direction-selective saturation of the quantum dot. The chiral spin-photon interface we demonstrate breaks reciproci…

Mechanical On-Chip Microwave Circulator

Nonreciprocal circuit elements form an integral part of modern measurement and communication systems. Mathematically they require breaking of time-reversal symmetry, typically achieved using magnetic materials and more recently using the quantum Hall effect, parametric permittivity modulation or Josephson nonlinearities. Here, we demonstrate an on-chip magnetic-free circulator based on reservoir engineered optomechanical interactions. Directional circulation is achieved with controlled phase-sensitive interference of six distinct electro-mechanical signal conversion paths. The presented circul…

Chiral Quantum Network with Giant Atoms

In superconducting quantum circuits (SQCs), chiral routing quantum information is often realized with the ferrite circulators, which are usually bulky, lossy and require strong magnetic fields. To overcome those problems, we propose a novel method to realize chiral quantum networks by exploiting giant atom effects in SQC platforms. By assuming each coupling point being modulated with time, the interaction becomes momentum-dependent, and giant atoms will chirally emit photons due to interference effects. The chiral factor can approach 1, and both the emission direction and rate can be freely tu…

Gyrator operation using Josephson mixers

Nonreciprocal microwave devices, such as circulators, are useful in routing quantum signals in quantum networks and protecting quantum systems against noise coming from the detection chain. However, commercial, cryogenic circulators, now in use, are unsuitable for scalable superconducting quantum architectures due to their appreciable size, loss, and inherent magnetic field. We report on the measurement of a key nonreciprocal element, i.e., the gyrator, which can be used to realize a circulator. Unlike state-of-the-art gyrators, which use a magneto-optic effect to induce a phase shift of $π$ b…

手性耦合到自旋腔的原子的纠缠生成与优化

Generation and optimization of entanglement between atoms chirally coupled to spin cavities

本文研究手性耦合到一维自旋腔的原子的纠缠生成与优化，发现宇称效应、经典驱动共振和受控无序可显著加速并增强纠缠，最高可比有序系统快四倍。

用于超导量子器件的参数控制手性界面

Parametrically controlled chiral interface for superconducting quantum devices

本文设计并实验实现了一种结合干涉与相位控制参数泵浦的超导量子比特手性界面，实现约30 dB方向性，并预测其无效率可低至百分之一量级。