Two-dimensional quantum walks of correlated photons

Abstract

Quantum walks in an elaborately designed graph are a powerful tool for simulating physical and topological phenomena, constructing novel quantum algorithms, and realizing universal quantum computing. Integrated photonics technology has emerged as a versatile platform for implementing a variety of quantum information tasks and as a promising candidate for performing large-scale quantum walks. Both extending physical dimensions and involving more particles will increase the complexity of the evolving systems. Pioneering studies have demonstrated a single particle walking on two-dimensional lattices and multiple walkers interfering on a one-dimensional structure. However, multiple particles evolving in a genuine two-dimensional space in a scalable fashion has remained a vacancy for nearly 10 years. We present a genuine two-dimensional quantum walk with correlated photons on a triangular photonic lattice, which is mapped to a 37 × 37 high-dimensional state space. The genuine two-dimensional quantum walk breaks through the physical restrictions of single-particle evolution, allowing for the encoding of information in large spaces and construction of high-dimensional graphs, which are beneficial for quantum information processing. Between the chip and the two-dimensional fanout interface, site-by-site addressing enables simultaneous detection of over 600 nonclassical interferences and observation of quantum correlations that violate a classical limit by 57 standard deviations. Our implementation provides a paradigm for multi-photon quantum walks in a two-dimensional configuration on a large scale, paving the way for practical quantum simulation and computation beyond the classical regime.

Quantum trajectories, interference, and state localisation in dephasing assisted quantum transport

“…Dephasing assisted transport is an example of stochastic resonance [17] where random fluctuations can amplify an otherwise low probability process. It has been well studied both experimentally [18][19][20][21][22] and theoretically [8,[24][25][26], including the exploring the effects of non-Markovian fluctuations in the dephasing terms [27].…”

Experimentally Detecting Quantized Zak Phases without Chiral Symmetry in Photonic Lattices

“…The two-band insulating system is built on a photonic chip under a continuous-time quantum walk framework. Waveguide lattices are a natural platform to study topological properties, both in the bulk and at the edges [17,18,[46][47][48][49]. The quantized Zak phase can be directly detected from bulk dynamics by means of the beam displacement method [29,39], while edge state dynamics can be visualized by boundary excitation of the lattice [18,39].…”

Quantum walks of two correlated photons in a 2D synthetic lattice

“…Hence, it can represent a powerful tool for the investigation of rich dynamics that are experimentally unexplored. Recent works reported 2D continuous-time quantum walks of correlated photons, relying on arrays of coupled waveguides (21,38,52) , and important results have been also achieved by means of superconductive quantum processors (6). We stress that our system is based on a very different approach, exploiting a synthetic 2D lattice made of internal modes of a single optical beam, as opposed to real-space neighbouring lattice sites, and implementing discrete-time evolutions that can be actively controlled and easily reconfigured.…”

“…Photonic platforms developed to implement QWs differ in terms of the methods to encode both walker and coin systems into optical degrees of freedom. Starting from the first experiments in linear optical interferometers composed of beamsplitters and phase shifters (33), integrated photonic technology has enabled significantly larger instances both in their continuoustime (21,26,(34)(35)(36)(37)(38) and discrete-time version (8,25,39,40). Other schemes rely on light polarization and orbital angular momentum degrees of freedom (9,41), multimode fibers (36) or fiber network loops (14,15,(42)(43)(44), where the walker position is simulated by the temporal separation between the laser pulses.…”

“…Other remarkable experiments have been conducted by controlling confined waves in arrays of micro-resonators (45,46). Multiparticle regimes have been already implemented in continuous-time QWs (47)(48)(49), even in 2D lattices (38). However, the demonstration of multi-photon discrete-time QWs in more than one spatial dimension has remained elusive thus far.…”