Most people think of diamonds as high-end adornments. Not Ania Bleszynski Jayich. The UC Santa Barbara physicist sees diamonds, which she grows in the UC Quantum Foundry, as a potentially powerful foundation for quantum sensors. Sensors are currently much farther along in their development than other potential quantum applications. Diamond sensors are particularly promising because diamonds require relatively few quantum bits (qubits) to operate, whereas a quantum computer, for instance, requires more than 100,000, perhaps as many as a million, qubits to handle error correction, one of the main hurdles for quantum computing.

A paper about the latest advance from the Bleszynski Jayich lab, “Spin-embedded diamond optomechanical resonator with a mechanical quality factor exceeding one million,” has been published in the journal Optica.

A University of Sydney quantum physicist has developed a new approach to quantum error correction that could significantly reduce the number of physical qubits required to build large-scale, fault-tolerant quantum computers. The study, co-authored by Dr. Dominic Williamson from the School of Physics, is titled “Low-overhead fault-tolerant quantum computation by gauging logical operators” and published in Nature Physics.

The work was done while Dr. Williamson was on a sabbatical working at global technology firm IBM in California. Elements of the new design have been integrated into IBM’s plan to build large-scale quantum computing.

“We’re at a point where theory and experiment are beginning to align,” Dr. Williamson said. “The big question now is how to design quantum computers that can be scaled efficiently to solve useful problems. Our work provides a promising blueprint.”

Quantum states are notoriously fragile, and can be destroyed simply through interactions, measurements, and exposure to their surrounding environments. In a new theoretical study published in Physical Review X, Rohan Mittal and colleagues at the University of Cologne have discovered a new way to protect quantum behavior on large scales within systems driven far from equilibrium. Their results could have promising implications for the design of more robust quantum devices.

When quantum many-body systems are driven out of equilibrium, they undergo decoherence, causing quantum correlations and superpositions to break down. Even when such a system is built from entirely quantum components, the effect can cause its behavior to become indistinguishable from that of a classical system on larger scales, making it unsuitable for technologies such as quantum computing or sensing.

So far, researchers have attempted to solve the decoherence problem by fine-tuning two independent parameters: one to push the system to the boundary between two distinct quantum phases, and another to ensure that quantum coherence is maintained at this boundary. In practice, however, the need to account for two parameters simultaneously has made this approach both fragile and experimentally daunting.