A New Method for Multi-Bit and Qudit Transfer Based on Commensurate Waveguide Arrays

TL;DR

This paper introduces a novel method leveraging engineered cross-talk in waveguide arrays to enable high-fidelity, parallel transfer of multi-bit and qudit states on optical chips, overcoming limitations of traditional optical interconnects.

Contribution

It presents an analytic approach to design waveguide arrays with commensurate eigenvalues for efficient multi-qubit and qudit transfer, including exact solutions for arrays of up to nine waveguides.

Findings

Exact solutions for waveguide arrays of up to nine waveguides.

Demonstration of periodic revivals enabling state transfer.

Discussion of fabrication limitations and practical implementation.

Abstract

The faithful state transfer is an important requirement in the construction of classical and quantum computers. While the high-speed transfer is realized by optical-fibre interconnects, its implementation in integrated optical circuits is affected by cross-talk. The cross-talk between densely packed optical waveguides limits the transfer fidelity and distorts the signal in each channel, thus severely impeding the parallel transfer of states such as classical registers, multiple qubits and qudits. Here, we leverage on the suitably engineered cross-talk between waveguides to achieve the parallel transfer on optical chip. Waveguide coupling coefficients are designed to yield commensurate eigenvalues of the array and hence, periodic revivals of the input state. While, in general, polynomially complex, the inverse eigenvalue problem permits analytic solutions for small number of waveguides. We present exact solutions for arrays of up to nine waveguides and use them to design realistic buses for multi-(qu)bit and qudit transfer. Advantages and limitations of the proposed solution are discussed in the context of available fabrication techniques.