[Paper Review] Chip-scale Simulations in a Quantum-correlated Synthetic Space

Usman A. Javid, Raymond Lopez‐Rios+4 more|arXiv (Cornell University)|Nov 2, 2022

Neural Networks and Reservoir Computing4 citations

TL;DR

This paper demonstrates a chip-scale quantum-correlated synthetic crystal using a dynamically modulated lithium niobate microresonator to generate a broadband quantum frequency comb with ~400×400 synthetic lattice modes. By leveraging time-frequency entanglement from spontaneous parametric down-conversion and on-chip electro-optic modulation, the system enables coherent control of quantum correlations to simulate quantum random walks, Bloch oscillations, and multi-level Rabi oscillations in the time-frequency domain.

ABSTRACT

An efficient simulator for quantum systems is one of the original goals for the efforts to develop a quantum computer [1]. In recent years, synthetic dimension in photonics [2] have emerged as a potentially powerful approach for simulation that is free from the constraint of geometric dimensionality. Here we demonstrate a quantum-correlated synthetic crystal, based upon a coherently-controlled broadband quantum frequency comb produced in a chip-scale dynamically modulated lithium niobate microresonator. The time-frequency entanglement inherent with the comb modes significantly extends the dimensionality of the synthetic space, creating a massive nearly 400 x 400 synthetic lattice with electrically-controlled tunability. With such a system, we are able to utilize the evolution of quantum correlations between entangled photons to perform a series of simulations, demonstrating quantum random walks, Bloch oscillations, and multi-level Rabi oscillations in the time and frequency correlation space. The device combines the simplicity of monolithic nanophotonic architecture, high dimensionality of a quantum-correlated synthetic space, and on-chip coherent control, which opens up an avenue towards chip-scale implementation of large-scale analog quantum simulation and computation [1,3,4] in the time-frequency domain.

Motivation & Objective

• To develop a scalable, chip-integrated platform for analog quantum simulation using synthetic dimensions in photonics.
• To overcome limitations of classical synthetic dimension platforms by utilizing non-classical quantum correlations between entangled photons.
• To achieve high-dimensional, electrically tunable quantum simulation in a monolithic nanophotonic architecture.
• To demonstrate practical quantum simulations—such as quantum random walks and Bloch oscillations—using on-chip generated entangled states.
• To enable large-scale quantum simulation in the time-frequency domain with minimal physical footprint and high coherence.

Proposed method

• Utilizes a coherently controlled quantum optical frequency comb (QOFC) generated via spontaneous parametric down-conversion (SPDC) in a periodically poled lithium niobate microresonator.
• Employs on-chip electro-optic modulators embedded within the resonator to induce nearest-neighbor coupling between comb modes, forming a tight-binding lattice.
• Leverages time-frequency entanglement between signal and idler photons to extend the synthetic dimensionality beyond classical frequency modes.
• Constructs a two-dimensional quantum-correlated synthetic lattice with nearly 400×400 modes via entanglement and coherent control.
• Employs spectral interferometry and joint spectral intensity (JSI) measurements to characterize quantum correlations and simulate dynamics.
• Uses numerical fitting and variance analysis to extract oscillation frequencies and quantify quantum walk spread from experimental data.

Experimental results

Research questions

• RQ1 Can a chip-scale photonic platform generate a high-dimensional quantum-correlated synthetic lattice using on-chip quantum frequency combs?
• RQ2 To what extent can time-frequency entanglement in a QOFC extend the effective dimensionality of a synthetic space beyond classical frequency modes?
• RQ3 Can on-chip electro-optic modulation enable coherent, tunable control over quantum correlations for simulating complex quantum dynamics?
• RQ4 Can this platform simulate non-trivial quantum phenomena such as quantum random walks and Bloch oscillations using entangled photon states?
• RQ5 How does the integration of quantum correlations and tunable coupling enable scalable analog quantum simulation in a monolithic nanophotonic platform?

Key findings

• The system generates a broadband quantum frequency comb with approximately 800 single-photon modes, forming a synthetic lattice of nearly 400×400 modes.
• Time-frequency entanglement between signal and idler photons enables long-range quantum correlations that significantly extend the effective dimensionality of the synthetic space.
• The device demonstrates a two-particle quantum random walk with a measured variance consistent with quantum dynamics, showing coherent spread in the joint spectral intensity (JSI) matrix.
• Bloch oscillations are observed in the time-frequency correlation space, with oscillation frequencies extracted via sinusoidal fitting of corrected coincidence histograms, achieving a 95% confidence interval.
• Multi-level Rabi oscillations are successfully simulated in the spectral and temporal correlation functions of the entangled photon pairs.
• The system achieves electrically tunable control over the synthetic lattice, enabling reconfigurable simulation of diverse quantum dynamics on a single chip.