Towards Implementation of Quantum Algorithms Using Electron and Nuclear Spins in Single Crystals

Abstract

Quantum computing set a goal to harness the quantum laws of physics and create computers more powerful than ever imagined. Different technologies can be chosen to implement quantum bits (qubits), each with their advantages and drawbacks. The idea of combining different technologies then seems natural in order to come up with an optimal quantum computer.

In this sense, Nuclear Magnetic Resonance (NMR) and Electron Spin Resonance (ESR) seem to be the perfect marriage. Indeed, while electron spins can perform quantum gates within nanoseconds, they have to fight very fast decoherence phenomena, the nuclear spins, on the other hand, require longer electromagnetic pulses to be rotated but can be controlled longer without loss of quantum information. Using electron spins as actuators and nuclear spins as memory then appears as the optimal use of this hybrid system. Another fact accounting for this association is that the control of the system through the electron spin requires techniques very similar to the well-known NMR ones.

This work focuses on characterizing as precisely as possible the Hamiltonian of a hybrid spin system in a solid-state single crystal, especially the electron-nuclear interactions, to perform high-fidelity control in a home-built pulsed ESR spectrometer. Using this knowledge, we show that we can choose the orientation of the magnetic field with respect to our crystal to obtain optimal experimental conditions. Indeed, with a good knowledge of the Hamiltonian of the system, we want demonstrate high-fidelity quantum control.

The final aim of this work is to dynamically supply highly polarized ancilla qubits that can be used in a Quantum Error Correction (QEC) experiment by implementing heat bath algorithmic cooling using a cold electron spin bath. This is an important step towards demonstrating the viability of spin systems for building quantum computers.