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A silicon quantum-dot-coupled nuclear spin qubit
摘要： Single nuclear spins in the solid state are a potential future platform for quantum computing, because they possess long coherence times and offer excellent controllability. Measurements can be performed via localized electrons, such as those in single atom dopants or crystal defects. However, establishing long-range interactions between multiple dopants or defects is challenging. Conversely, in lithographically defined quantum dots, tunable interdot electron tunnelling allows direct coupling of electron spin-based qubits in neighbouring dots. Moreover, the compatibility with semiconductor fabrication techniques may allow for scaling to large numbers of qubits in the future. Unfortunately, hyperfine interactions are typically too weak to address single nuclei. Here we show that for electrons in silicon metal–oxide–semiconductor quantum dots the hyperfine interaction is sufficient to initialize, read out and control single 29Si nuclear spins. This approach combines the long coherence times of nuclear spins with the flexibility and scalability of quantum dot systems. We demonstrate high-fidelity projective readout and control of the nuclear spin qubit, as well as entanglement between the nuclear and electron spins. Crucially, we find that both the nuclear spin and electron spin retain their coherence while moving the electron between quantum dots. Hence we envision long-range nuclear–nuclear entanglement via electron shuttling. Our results establish nuclear spins in quantum dots as a powerful new resource for quantum processing.
关键词： entanglement,hyperfine interaction,nuclear spins,quantum dots,silicon,coherence times,quantum computing
更新于2025-09-12 10:27:22
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Spin properties of NV centers in high-pressure, high-temperature grown diamond
摘要： The sensitivity of magnetic and electric field sensors based on nitrogen-vacancy (NV) center in diamond strongly depends on the available concentration of NV and their coherence properties. Achieving high coherence times simultaneously with high concentration is a challenging experimental task. Here, we demonstrate that by using a temperature gradient method of high-pressure, high-temperature growing technique, one can achieve nearly maximally possible dephasing T2* times, limited only by carbon nuclear spins at low nitrogen concentrations or nitrogen electron spin at high nitrogen concentrations. Hahn-echo T2 coherence times were also investigated and found to demonstrate reasonable values. Thus, the high-pressure, high-temperature technique is a strong contender to the popular chemical vapor deposition method in the development of high-sensitivity, diamond-based sensors.
关键词： carbon nuclear spins,diamond-based sensors,NV centers
更新于2025-09-09 09:28:46
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Single-beam resonant spin amplification of electrons interacting with nuclei in a GaAs/(Al,Ga)As quantum well
摘要： The dynamic polarization of nuclear spins interacting with resident electrons under resonant excitation of trions is studied in a nominally undoped GaAs/(Al,Ga)As quantum well. Unlike in common time-resolved pump-probe techniques, we used a single-beam approach in which the excitation light is modulated between the circular and linear polarization states. The time-integrated intensity of the excitation laser re?ected from the sample surface, proportional to the optical generation rate and changing due to the pumping of the resident electrons, is detected. Polarized electrons, on the other hand, transfer their spin to the lattice nuclei via the hyper?ne interaction. Exciting the sample with a train of pulses in an external magnetic ?eld leads to resonant spin ampli?cation observed when the Larmor precession frequency is synchronized with the laser pulse repetition rate. A buildup of the nuclear spin polarization causes a shifting of the resonant spin ampli?cation peaks since the resulting nuclear ?eld alters the strength of the external magnetic ?eld experienced by the electrons. It was established that the nuclear spin polarization time T1 is temperature dependent and, owing to the electron localization at lower temperatures, becomes shorter. “Locking” of the nuclear (Overhauser) ?eld in the oblique external magnetic ?eld, related to the anisotropy of the electron g factor, was observed. The g factor ratio between the in-plane (g(cid:2)) and out-of-plane (g⊥) components was estimated to be g⊥/g(cid:2) = 1.3.
关键词： hyper?ne interaction,resonant spin ampli?cation,resonant excitation,electron g factor,quantum well,dynamic polarization,single-beam approach,nuclear spins
更新于2025-09-09 09:28:46