Fraunhofer IWU and SAXON Q report an 87.0% success probability for finding two marked states in an eight-state search, exceeding the 46.4% classical limit on a commercial, room-temperature quantum computer. The demonstration, performed at an average temperature of 296.3 Kelvin in open air, contrasts sharply with cryogenic systems requiring tens of kilowatts of power.
Researchers utilized nitrogen-14 and carbon-13 nuclei as qubits, retaining quantum state for milliseconds, roughly a thousand times longer than the system’s electron spin used for read/write operations. This approach, detailed on arXiv, exercises a full stack of gates with Grover’s algorithm, a standard stress test for quantum processors.
Three-Qubit Grover Search Achieves 87% Success on Room-Temperature Diamond
Achieving an 87.0% success probability, a three-qubit Grover search performed by SAXON Q IWU located two target states within an eight-state problem, exceeding the 46.4% limit possible with classical computers. This demonstration used a commercial quantum computer operating at 296.3 Kelvin, a standard room temperature, and in open air, a stark contrast to the cryogenic conditions demanded by many competing systems. The only published result higher, 89.4% on a silicon spin qubit processor, required temperatures of 15 millikelvin and readout post-selection.
The system’s qubits were not based on electron spins, a common approach, but instead used the nuclear spins of nitrogen-14 and two carbon-13 nuclei embedded within a diamond lattice. This extended coherence is attributed to the shielding effect of the surrounding carbon lattice, providing a stable environment for quantum information storage.
Single-qubit gate fidelities reached 99.98%, with an average single-qubit Clifford fidelity of 99.90%, while two-qubit subspace gate fidelities averaged 95.7%. Grover’s algorithm was selected as a benchmark because it provides a quadratic speedup over classical search methods and rigorously tests the full stack of quantum gates.
The IWU and SAXON Q system operates much like a solid-state ion trap, eliminating the need for vacuum pumps, cryostats, or optical traps required by trapped-ion systems, which have previously demonstrated 44 to 69% success rates in similar searches, the company says. The full details of this work are available on Arxiv.org.
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