Coherent control of single spins in silicon carbide at room temperature

Vacancy-related centres in silicon carbide are attracting growing attention because of their appealing optical and spin properties. These atomic-scale defects can be created using electron or neutron irradiation; however, their precise engineering has not been demonstrated yet. Here, silicon vacancies are generated in a nuclear reactor and their density is controlled over eight orders of magnitude within an accuracy down to a single vacancy level. An isolated silicon vacancy serves as a near-infrared photostable single-photon emitter, operating even at room temperature. The vacancy spins can be manipulated using an optically detected magnetic resonance technique, and we determine the transition rates and absorption crosssection, describing the intensity-dependent photophysics of these emitters. The on-demand engineering of optically active spins in technologically friendly materials is a crucial step toward implementation of both maser amplifiers, requiring high-density spin ensembles, and qubits based on single spins.

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“…Using a solid immersion lens, a count rate of 4 Â 10 4 c.p.s. has been achieved 40 , supporting the conclusions drawn here.…”

Section: Discussionsupporting

confidence: 89%

“…Note, when the manuscript was in the reviewing process, we learnt about two papers where the coherent control of single spins in SiC is reported 39,40 . Using a solid immersion lens, a count rate of 4 Â 10 4 c.p.s.…”

Section: Discussionmentioning

confidence: 99%

Engineering near-infrared single-photon emitters with optically active spins in ultrapure silicon carbide

et al. 2015

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“…We showed that this feedback-based protection algorithm can protect the qubit coherence far beyond the dephasing time of the qubit, even if no active control is applied to decouple it from the noise. The algorithm can be extended to applications in quantum information processing and quantum sensing, and it could be implemented in many other hybrid spin systems, such as phosphorus [27] or antimony [28] donors in silicon, defects in silicon carbide [29] or quantum dots [30]. As we applied a coherent feedback protocol, thus avoiding measuring the state of the ancilla, the decoherent effects of the bath are effectively stored in the ancilla.…”

Section: Figmentioning

confidence: 99%

Coherent feedback control of a single qubit in diamond

Hirose

Cappellaro

2016

Nature

103

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Engineering desired operations on qubits subjected to the deleterious effects of their environment is a critical task in quantum information processing, quantum simulation and sensing. The most common approach is to rely on open-loop quantum control techniques, including optimal control algorithms, based on analytical [1] or numerical [2] solutions, Lyapunov design [3] and Hamiltonian engineering [4]. An alternative strategy, inspired by the success of classical control, is feedback control [5]. Because of the complications introduced by quantum measurement [6], closed-loop control is less pervasive in the quantum settings and, with exceptions [7,8], its experimental implementations have been mainly limited to quantum optics experiments. Here we implement a feedback control algorithm with a solid-state spin qubit system associated with the Nitrogen Vacancy (NV) centre in diamond, using coherent feedback [9] to overcome limitations of measurement-based feedback, and show that it can protect the qubit against intrinsic dephasing noise for milliseconds. In coherent feedback, the quantum system is connected to an auxiliary quantum controller (ancilla) that acquires information about the system's output state (by an entangling operation) and performs an appropriate feedback action (by a conditional gate). In contrast to open-loop dynamical decoupling (DD) techniques [10], feedback control can protect the qubit even against Markovian noise and for an arbitrary period of time (limited only by the ancilla coherence time), while allowing gate operations. It is thus more closely related to Quantum Error Correction schemes [11][12][13][14], which however require larger and increasing qubit overheads. Increasing the number of fresh ancillas allows protection even beyond their coherence time. We can further evaluate the robustness of the feedback protocol, which could be applied to quantum computation and sensing, by exploring an interesting tradeoff between information gain and decoherence protection, as measurement of the ancilla-qubit correlation after the feedback algorithm voids the protection, even if the rest of the dynamics is unchanged.To demonstrate coherent feedback with spin qubits, we choose two of the most common tasks for qubits, implementing the no-operation (NOOP) and NOT gates, while cancelling the effects of noise. A simple, measurementbased feedback scheme, exploiting one ancillary qubit, was proposed in [16]. The correction protocol (Fig. 1a) works by entangling the qubit-ancilla system before the desired gate operation. By selecting an entangling operation U c appropriate for the type of bath acting on the system, information about the noise action is encoded in the ancilla state. After undoing the entangling operation, the qubit coherence can be restored by a feedback action, Hadamard gates prepare and read out a superposition state of the qubit, |φ q = 1 √ 2 (|0 + |1 ). Amid entangling gates between qubit and ancilla, the qubit is subjected to noise (and possibly unitary gates U ). We assume the ancil...

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“…It is both an industrially important substrate for high-performance electronic devices [1] and a host to several types of vacancy-related paramagnetic color centers with remarkable attributes . Much like the diamond nitrogen-vacancy center [24,25], these color centers have electronic spin states that can be addressed at either ensemble or single-spin levels [18,19] through optically detected magnetic resonance (ODMR). Moreover, spin coherence times can exceed 1 ms [18], and ODMR can persist up to room temperature [10,11,14,19].…”

mentioning

confidence: 99%

“…Much like the diamond nitrogen-vacancy center [24,25], these color centers have electronic spin states that can be addressed at either ensemble or single-spin levels [18,19] through optically detected magnetic resonance (ODMR). Moreover, spin coherence times can exceed 1 ms [18], and ODMR can persist up to room temperature [10,11,14,19]. Although the fluctuating nuclear spin bath is a principal source of electronic spin decoherence in these types of systems [26], nuclear spins in SiC are not purely detrimental.…”

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confidence: 99%

Polarizing Nuclear Spins in Silicon Carbide

Cappellaro

2015

Physics

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We demonstrate optically pumped dynamic nuclear polarization of 29 Si nuclear spins that are strongly coupled to paramagnetic color centers in 4H-and 6H-SiC. The 99% AE 1% degree of polarization that we observe at room temperature corresponds to an effective nuclear temperature of 5 μK. By combining ab initio theory with the experimental identification of the color centers' optically excited states, we quantitatively model how the polarization derives from hyperfine-mediated level anticrossings. These results lay a foundation for SiC-based quantum memories, nuclear gyroscopes, and hyperpolarized probes for magnetic resonance imaging. DOI: 10.1103/PhysRevLett.114.247603 PACS numbers: 76.70.Fz, 61.72.jn, 71.55.-i, 76.30.Mi Silicon carbide is a promising material for quantum electronics at the wafer scale. It is both an industrially important substrate for high-performance electronic devices [1] and a host to several types of vacancy-related paramagnetic color centers with remarkable attributes . Much like the diamond nitrogen-vacancy center [24,25], these color centers have electronic spin states that can be addressed at either ensemble or single-spin levels [18,19] through optically detected magnetic resonance (ODMR). Moreover, spin coherence times can exceed 1 ms [18], and ODMR can persist up to room temperature [10,11,14,19]. Although the fluctuating nuclear spin bath is a principal source of electronic spin decoherence in these types of systems [26], nuclear spins in SiC are not purely detrimental. If polarized and controlled, they would be a technologically valuable resource.In this Letter, we show that near-infrared light can nearly completely polarize populations of 29 Si nuclear spins in SiC. In this dynamic nuclear polarization (DNP) [27,28] process, the optically pumped polarization of electron spins bound to either neutral divacancy [4,5,8,10,14] or PL6 [10,14,16] color centers is transferred to proximate nuclei via the hyperfine interaction. Optically polarizing nuclei in SiC is experimentally straightforward, requiring only broadband illumination and a small external magnetic field (300-500 G), with which we tune color-center ensembles to their ground-state (GS) or excited-state (ES) spin-level anticrossings (the GSLAC and ESLAC, respectively). Optically pumping crystals has previously led to roomtemperature DNP in napthalene [29], diamond [30][31][32][33][34][35], and GaNAs [36]. Our results show that room-temperature DNP can be efficiently driven in a material that plays a leading role in the semiconductor industry.We find that SiC color centers can mediate a high degree (>85%) of ESLAC-derived nuclear polarization from at least 5 to 298 K, a surprisingly broad temperature range for this mechanism. This robust DNP could be applied to initialize quantum memories in quantumcommunication technologies, especially since the color centers are telecom-range emitters, with narrow optical linewidths at low temperatures [16,21,37]. Other applications of DNP, including solid-state nuclear gyroscopes [38,39...

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Coherent control of single spins in silicon carbide at room temperature

Cited by 581 publications

References 36 publications

Engineering near-infrared single-photon emitters with optically active spins in ultrapure silicon carbide

Engineering near-infrared single-photon emitters with optically active spins in ultrapure silicon carbide

Coherent feedback control of a single qubit in diamond

Polarizing Nuclear Spins in Silicon Carbide

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