Quantum logic gates from time-dependent global magnetic field in a system with constant exchange

TL;DR

This paper presents a method for implementing universal quantum gates in a two-electron system with constant exchange interaction by using time-dependent magnetic fields and optimal control, avoiding strong magnetic pulses.

Contribution

It introduces a novel approach to perform quantum gates by modulating magnetic field amplitude in a system with constant exchange, utilizing optimal control algorithms.

Findings

Numerical experiments show effective single- and two-qubit gate implementation.

Small magnetic field changes suffice for resonance-based qubit control.

The method avoids the need for strong magnetic field pulses.

Abstract

We propose a method for implementation of an universal set of one- and two-quantum-bit gates for quantum computation in the system of two coupled electrons with constant non-diagonal exchange interaction. Suppression of the exchange interaction is offered to implement by all-the-time repetition of single spin rotations. Small g-factor difference of electrons allows to address qubits and to avoid strong magnetic field pulses. It is shown by means of numerical experiments that for implementation of one- and two-qubit operations it is sufficient to change the amplitude of the magnetic field within a few Gauss, introducing in a resonance one and then the other electron. To find the evolution of the two-qubit system, we use the algorithms of the optimal control theory.