Overcoming the vulnerability of qubits (basic units of quantum information processing) was an issue for the realization of quantum computers and quantum cryptography, but the nitrogen vacancy center (NV center: nitrogen atom replaced by carbon atom) in diamond , The spin qubit existing in the structure adjacent to the vacancy lacking one carbon atom) has been regarded as promising from the viewpoint of operation accuracy and information retention time.

　In the study, the magnetic field was completely eliminated, and upward and downward spins with no energy difference were used as qubits.Operation is difficult because there is no energy difference, but it is resistant to operation errors and environmental noise.The research group proposed to apply "polarized microwaves" from two orthogonal wires to a spin qubit in the center of NV, which is stable even at room temperature, and perform quantum manipulation geometrically. We succeeded in the experiment of the basic unit of calculation of quantum information). This spin qubit manipulation method, named "geometric qubit", can eliminate the problematic error and virtually eliminate the limit of manipulation accuracy.

　The results of this time are universal quantum computers and quantum simulators that operate at room temperature, quantum relay (means for sending quantum information to distant places where photons cannot reach), quantum sensing, and quantum measurement, which are indispensable for connecting these to networks by quantum cryptographic communication. It is expected to pave the way for the realization of all quantum information elements such as IoT security devices.

Paper information:[Nature Communications] “Universal holonomic quantum gates over geometric spin qubits with polarised microwaves”