Researchers at UC Santa Barbara, led by physicist Ania Bleszynski Jayich, are developing diamond-based quantum sensors. Their latest advance, detailed in the journal Optica, involves a spin-embedded diamond optomechanical resonator.
The Promise of Diamond in Quantum Sensing
Diamonds are considered promising for quantum sensing due to their efficiency, requiring relatively few quantum bits (qubits) compared to quantum computers.
The Diamond Optomechanical Resonator
The team's diamond optomechanical crystal, a thin beam approximately one micrometer wide, was engineered to resonate. A telecom frequency optical resonator is co-located to assist in driving and reading the mechanical degree of freedom.
High Performance: A Million-Plus Q Factor
The resonator achieved a mechanical quality (Q) factor exceeding one million. Operating at 10-gigahertz-scale frequencies, the oscillator cycles its signal 10 billion times per second.
A high Q factor indicates the system can oscillate for a long duration before energy dissipates, crucial for storing quantum information.
Nitrogen Vacancy (NV) Centers: The Quantum Sensors
Engineered defects within the diamond, known as nitrogen vacancy (NV) centers, function as quantum sensors. These NV centers, physically housed inside the diamond lattice, fluoresce when excited by light and serve as long-lived qubits capable of sensing tiny magnetic, electric, strain, or thermal fields.
Enabling Qubit Interaction
A long-term objective is to facilitate interaction between these hundreds of qubits. The coordinated motion of atoms in the lattice provides a pathway for these embedded defects to interact, with the high Q factor enabling stronger mediation and control over this interaction.
This quantum advantage could lead to improved precision in sensing.
Diamond's Unique Advantages
While silicon and silicon-nitride are common materials for quantum mechanical systems, diamond offers distinct advantages. These include highly coherent qubits, high thermal conductivity, a wide band gap, and notable optical and mechanical properties. The lab has successfully addressed many fabrication challenges associated with diamond.
Next Steps: Achieving Even Higher Q Factors
Currently, the Q factor measurements were conducted using continuous optical probing, which causes heating due to light absorption.
Future research aims to use pulsed optical probing, where measurements are taken when the light is off, to potentially achieve significantly improved Q factors comparable to or exceeding silicon.
The Ultimate Goal
Ultimately, the researchers intend to leverage higher mechanical Q factors to enable mechanically mediated NV-NV qubit interactions, aiming to realize a many-body, metrologically useful entangled state.