Scientists Achieve Record-Breaking Coherence Times in Solid-State Nuclear Spin Qubits

Record-Breaking Quantum Coherence Achieved

Scientists have reportedly achieved a major breakthrough in quantum computing with individual solid-state nuclear spin qubits demonstrating coherence times exceeding seconds, according to research published in Nature Physics. Sources indicate this represents more than an order of magnitude improvement over previous records and positions nuclear spins as promising candidates for quantum memory and processing applications.

Record-Breaking Quantum Coherence Achieved
Novel Quantum Control Methods
Quantum Non-Demolition Readout
Unprecedented Coherence Times
Material Advantages and Future Prospects
Technical Implementation Details

Novel Quantum Control Methods

Unlike previous approaches that relied on direct radio-frequency driving or coupled electron-nuclear dynamics, researchers developed an innovative method using stimulated Raman transitions. The report states this technique enables all-microwave single- and two-nuclear-spin-qubit gates without populating the electron spin excited state. Analysts suggest this approach overcomes previous limitations caused by resonator suppression of low-frequency drives and weak direct coupling between spins and antennas.

Quantum Non-Demolition Readout

The research team implemented sophisticated detection methods for nuclear spin states, according to the published findings. By repeatedly exciting the electron spin at four distinct frequencies and detecting emitted photons, scientists achieved quantum non-demolition readout with state probabilities ranging from 0.91 to 0.95. The report indicates this high-fidelity detection capability was crucial for characterizing qubit performance and verifying quantum operations.

Unprecedented Coherence Times

Researchers measured remarkable coherence characteristics using unconditional Raman driving, with free-induction decay times of 0.8 seconds for Qb1 and 1.2 seconds for Qb2. These times reportedly surpass previous records by more than an order of magnitude and rival those measured in isotopically enriched materials. Hahn echo measurements further revealed coherence times of 3.4 seconds and 4.4 seconds for the two qubits respectively, suggesting strong potential for practical quantum applications., according to industry experts

Material Advantages and Future Prospects

The experiments were conducted using erbium-doped calcium tungstate (Er:CaWO₄) crystals, which analysts suggest offer significant advantages for spin-based quantum computing. The report states that the observed coherence times in this natural-abundance material compete with those in specially engineered systems. Researchers believe that dynamically detuning the resonator during pulse sequences while employing dynamical decoupling could further extend these coherence times, potentially opening new avenues for quantum information processing.

Technical Implementation Details

According to the published methodology, the team used stimulated Raman transitions driven by two simultaneous microwave tones at different frequencies. This approach reportedly enabled high-fidelity nuclear spin qubit rotations while avoiding population of electron spin excited states. The research demonstrates that virtual transitions through electron excited states allow for narrow resonance linewidths of approximately 100 Hz, two orders of magnitude narrower than electron spin linewidths.

The breakthrough represents significant progress toward practical quantum computing systems, with researchers noting that the combination of long coherence times and high-fidelity control operations positions nuclear spins as viable building blocks for future quantum technologies.