Community Research and Development Information Service - CORDIS

H2020

NAMESTRANSIS — Result In Brief

Project ID: 707364
Funded under: H2020-EU.1.3.2.
Country: Netherlands
Domain: Fundamental Research , Industrial Technologies, Digital Economy

A nanoscale device that couples light and mechanical motion has quantum computing potential

EU-funded scientists developed a silicon-based nanoscale optomechanical device that allows for record strong coupling between mechanical motion and light. They envision using it as a quantum transducer between spin quantum bits and light, a prospect that could advance significantly the goal of silicon-based quantum computers.
A nanoscale device that couples light and mechanical motion has quantum computing potential
Manipulation of quantum effects in materials is becoming more powerful leading to technological devices with fundamentally superior performance and capabilities. Electrons bound to donors in silicon have recently been reported to have one of the longest quantum coherence times. In particular, phosphorous impurity atoms in silicon are one of the most extensively studied atoms that retain their spin coherence – that is the time it takes for the quantum state to be destroyed by the environment.

Spin information converted to light signals

To build a functional quantum computer, it is necessary to control a great number of qubits and effectively read out and communicate the qubit states. Tiny optomechanical structures could become a critical part of the progress in quantum information in the near future. “Nanoscale optomechanical resonators can serve as excellent ‘quantum transducers’ between differing systems, like microwaves and light, or qubits and light, namely acting like a conduit of quantum information between these separate systems,” notes Dr Juha Muhonen, the funded fellow of NAMESTRANSIS, a Marie Skłodowska-Curie Action project.

The main motivation was to create a silicon-based optomechanical device that could allow for coupling the electron spin into the quantised motion of a nanoscale optomechanical resonator, where the motion of this tiny structure is in turn coupled to optical photons. “Embedding phosphorous impurity atoms in a wafer of silicon and then encoding information in the spin of the associated electrons can be used to store quantum information,” explains Dr Muhonen. “Strong coupling interactions between the mechanical motion of the resonator and light could then be responsible for the readout and communication of the quantum information,” adds Dr Muhonen.

Unrivalled performance

The project team studied a special kind of optomechanical resonator – a ‘sliced photonic crystal nanobeam cavity’ – that displayed conversion of small vibrational displacements to light with unprecedented strength.

Project work has thus been not only theoretically and practically challenging, but also rewarding. “We have noticed that our optomechanical device behaved in new ways that did not match the currently used analytical models. This strong optomechanical coupling was attributed to the fact that the cavity can confine light to scales much smaller than the optical wavelength. The system demonstrated nonlinear effects that pronouncedly impacted the optical response, mechanical displacement measurement and radiation pressure,” outlines Prof. Verhagen, the leader of the group where the project was performed.

The project team demonstrated a new measurement method of the resonator motion based on fast light pulses. “Using very fast light pulses allows the measurements to be ‘back-action-evading’, and opens up the possibility for testing the quantum nature of the mechanical motion by creating non-classical mechanical states”, explains Dr Muhonen. Besides that, fast light pulses can help make quantum sensing devices even more sensitive, or could be used for fast and accurate spin readout in the future quantum transducer.

Optical readout and communication of spin states in silicon as well as the creation of non‐classical mechanical states are both long‐standing goals of researchers in the field. The project successfully demonstrated how the newly developed silicon-based nanoscale device can measure tiny mechanical movements with high accuracy and has a high potential to advance both of these goals.

Besides quantum information, applications also include force sensors, gas sensors and accelerometers.

Keywords

NAMESTRANSIS, silicon, quantum information, qubits, coupling, electron spin, optomechanical resonator, nanomechanical motion, quantum computing, phosphorous impurity, quantum sensing
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