Three-dimensional entanglement on a silicon chip

Liangliang Lu,Leizhen Chen,Xinlun Cai,Yanqing Lu,Tonghua Yu,Shining Zhu,Zhiyu Chen,Wenchao Ma,Lijun Xia,Xiao-Song Ma,Ying Pan,Tao Tao

doi:10.1038/s41534-020-0260-x

Abstract

Entanglement is a counterintuitive feature of quantum physics that is at the heart of quantum technology. High-dimensional quantum states offer unique advantages in various quantum information tasks. Integrated photonic chips have recently emerged as a leading platform for the generation, manipulation and detection of entangled photons. Here, we report a silicon photonic chip that uses interferometric resonance-enhanced photon-pair sources, spectral demultiplexers and high-dimensional reconfigurable circuitries to generate, manipulate and analyse path-entangled three-dimensional qutrit states. By minimizing on-chip electrical and thermal cross-talk, we obtain high-quality quantum interference with visibilities above 96.5% and a maximally entangled-qutrit state with a fidelity of 95.5%. We further explore the fundamental properties of entangled qutrits to test quantum nonlocality and contextuality, and to implement quantum simulations of graphs and high-precision optical phase measurements. Our work paves the path for the development of multiphoton high-dimensional quantum technologies.

Highlights

Entanglement is a central resource for quantum-enhanced technology, including quantum computation[1], communication[2] and metrology[3]
Quantum states span the Hilbert space with a dimensionality of dn, where d is the dimensionality of a single particle and n is the number of particles in the entangled states
Most of the widely used quantum information processing protocols are based on qubits, a quantum system with d = 2

Summary

INTRODUCTION

Entanglement is a central resource for quantum-enhanced technology, including quantum computation[1], communication[2] and metrology[3]. The generation of high-dimensional path-entangled photon pairs typically requires the simultaneous operation of several coherently pumped indistinguishable photon-pair sources and several multi-path interferometers with high phase stability[25]. Recent advances of on-chip high-dimensional entanglement have employed frequency-encoding generated from a micro-resonator photon-pair source[17] and path-encoding generated from meander waveguides photon-pair source[20]. We employ a silicon photonic chip using an advanced resonator source embedded in Mach-Zehnder interferometers (MZIs) to generate, manipulate and characterize pathentangled qutrits (d = 3). This narrow-band feature provides high-quality single photons, and holds the promise for direct coupling with telecom quantum memory[33], which is not possible for the nanowire source due to the prohibitive low count rate after ~GHz bandwidth filtering. Each qutrit can be locally manipulated by a 3D-MP24, which is composed of thermo-optic phase shifters (PSs) and multi-mode

RESULTS

Result

CCab max value j dCCab dφ j is

Findings

DISCUSSION