Takaaki Shimo-Oka

Towards realizing a quantum memory for a superconducting qubit: storage and retrieval of quantum states.

We have built a hybrid system composed of a superconducting flux qubit (the processor) and an ensemble of nitrogen-vacancy centers in diamond (the memory) that can be directly coupled to one another, and demonstrated how information can be transferred from the flux qubit to the memory, stored, and subsequently retrieved. We have established the coherence properties of the memory and succeeded in creating an entangled state between the processor and memory, demonstrating how the entangled states coherence is preserved. Our results are a significant step towards using an electron spin ensemble as a quantum memory for superconducting qubits.

Observation of dark states in a superconductor diamond quantum hybrid system.

The hybridization of distinct quantum systems has opened new avenues to exploit the best properties of these individual systems. Superconducting circuits and electron spin ensembles are one such example. Strong coupling and the coherent transfer and storage of quantum information has been achieved with nitrogen vacancy centres in diamond. Recently, we have observed a remarkably sharp resonance (~1 MHz) at 2.878 GHz in the spectrum of flux qubit negatively charged nitrogen vacancy diamond hybrid quantum system under zero external magnetic field. This width is much narrower than that of both the flux qubit and spin ensemble. Here we show that this resonance is evidence of a collective dark state in the ensemble, which is coherently driven by the superposition of clockwise and counter-clockwise macroscopic persistent supercurrents flowing in the flux qubit. The collective dark state is a unique physical system and could provide a long-lived quantum memory.

Improving the lifetime of the NV center ensemble coupled with a superconducting flux qubit by applying magnetic fields

One of the promising systems to realize quantum computation is a hybrid system where a superconducting flux qubit plays the role of a quantum processor and the nitrogen-vacancy-

Optically detected magnetic resonance of high-density ensemble of NV(-) centers in diamond.

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Hybrid quantum magnetic-field sensor with an electron spin and a nuclear spin in diamond

center ensemble is used as a quantum memory. We have theoretically and experimentally studied the effect of magnetic fields on this hybrid system, and found that the lifetime of the vacuum Rabi oscillation is improved by applying a few mT magnetic field to the

Control of coherence among the spins of a single electron and the three nearest neighbor 13C nuclei of a nitrogen-vacancy center in diamond

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Publisher Correction: Observation of dark states in a superconductor diamond quantum hybrid system

center ensemble. Here, we construct a theoretical model to reproduce the vacuum Rabi oscillations with and without magnetic fields applied to the

Fast phase manipulation of the single nuclear spin in solids by rotating fields

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Hybridization of superconducting flux qubits and diamond ensembles

centers, and we determine the reason why magnetic fields can affect the coherent properties of the

Hybrid system composed of a superconducting flux qubit and an electron spin ensemble in diamond: A theoretical analysis

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