In an exciting development in the field of quantum technology, a team of researchers from MIT and other institutions has made a significant breakthrough that could enhance the capabilities of quantum sensing devices.
These devices have the potential to revolutionize various applications, from detailed brain imaging to highly accurate air traffic control systems, by utilizing the principles of quantum mechanics for measurement with unprecedented precision.
At the heart of this advancement is the innovative use of microscopic defects within diamonds, known as “qubits,” which are the fundamental components of quantum devices.
By focusing on these defects, specifically the nitrogen-vacancy (NV) centers in diamonds, the researchers have developed a technique to identify and control a greater number of qubits.
This method significantly improves the sensitivity of quantum sensing by enabling the construction of larger quantum registers, which are collections of qubits that work together to perform quantum sensing.
The research team’s approach builds on the ability to detect and excite NV centers using laser light, followed by controlling them with microwave pulses.
They introduced a new protocol involving microwave pulses to identify and manipulate additional defects, referred to as dark spins, which are not visible with laser light.
By starting with a central NV spin, the researchers created chains of controlled spins, extending their reach to spins beyond the direct sensing capability of the NV center.
This method of extending control to dark spins involves locating them through a connected network of spins, starting from the NV center and branching out.
The process uses a technique known as spin echo double resonance (SEDOR), which decouples the NV center from all interacting spins, then selectively pairs it with a nearby spin.
This pairing allows the researchers to transfer polarization from the NV center to the first-layer spin, and then from there, to additional spins in the chain.
Alex Ungar, a PhD student at MIT and lead author of the paper published in PRX Quantum, emphasized the exploratory nature of their work, highlighting the potential to discover more advantageous qubits by venturing into previously unexplored areas.
The research team, which includes experts from the University of Waterloo, Oak Ridge National Laboratory, Brookhaven National Laboratory, Stony Brook University, and the University of Illinois at Urbana-Champaign, demonstrated the possibility of controlling a chain of three qubits and estimated that their technique could scale to control even longer chains or higher-layer spins, potentially accessing hundreds of qubits.
The success of this technique depends on the precise application of microwave pulses, which must closely match the resonance frequency of the targeted spins.
The researchers have optimized their protocol to overcome challenges posed by environmental instability, such as temperature fluctuations and vibrations, that can affect the accuracy of their measurements.
This breakthrough sets the stage for building larger quantum registers, which could significantly enhance the performance of quantum sensors.
The team plans to continue refining their technique to characterize and probe other electronic spins and explore different types of defects that could serve as qubits.
Supported by the U.S. National Science Foundation and the Canada First Research Excellence Fund, this research represents a leap forward in the quest to harness the full potential of quantum sensing technologies.
The research findings can be found in PRX Quantum.
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