Quantum state transfer with untuneable couplings

TL;DR

This paper introduces a flexible quantum state transfer method that does not require switching qubit couplings, using only bias control, enabling efficient multi-state transmission with minimal control lines.

Contribution

The authors propose a novel bias-controlled quantum state transfer scheme that operates without switching couplings, allowing multiple states transfer and simplified control.

Findings

Perfect state transfer achieved with fixed and variable parameters.

Transmission of multiple quantum states with only two qubit separation.

Reduced control lines needed for classical information transfer.

Abstract

We present a general scheme for implementing bi-directional quantum state transfer in a quantum swapping channel. Unlike many other schemes for quantum computation and communication, our method does not require qubit couplings to be switched on and off. The only control variable is the bias acting on individual qubits. We show how to derive the parameters of the system (fixed and variable) such that perfect state transfer can be achieved. Since these parameters vary linearly with the pulse width, our scheme allows flexibility in the time scales under which qubits evolve. Unlike quantum spin networks, our scheme allows the transmission of several quantum states at a time, requiring only a two qubit separation between quantum states. By pulsing the biases of several qubits at the same time, we show that only eight bias control lines are required to achieve state transfer along a channel of arbitrary length. Furthermore, when the information to be transferred is purely classical in nature, only three bias control lines are required, greatly simplifying the circuit complexity.