General theory of feedback control of a nuclear spin ensemble in quantum dots

Yang, Wen; Sham, L. J.

doi:10.1103/physrevb.88.235304

Cited by 29 publications

(46 citation statements)

References 106 publications

(323 reference statements)

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“…For instance, solid-state quantum memories, a vital component for quantum information technologies, count on the long coherence times of nuclear spins [3]. In addition to storing the quantum state, nuclear spins potentially can act as the central processing unit as in ensemble computing [23,24] that can also be extended to quadrupolar nuclei [25], or, they can present an ideal test bed for quantum control as an integral part of an exciton-nuclei feedback loop [5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Nuclear magnetic resonance inverse spectra of InGaAs quantum dots: Atomistic level structural information

2014

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A wealth of atomistic information is contained within a self-assembled quantum dot (QD), associated with its chemical composition and the growth history. In the presence of quadrupolar nuclei, as in InGaAs QDs, much of this is inherited to nuclear spins via the coupling between the strain within the polar lattice and the electric quadrupole moments of the nuclei. Here, we present a computational study of the recently introduced inverse spectra nuclear magnetic resonance technique to assess its suitability for extracting such structural information. We observe marked spectral differences between the compound InAs and alloy InGaAs QDs. These are linked to the local biaxial and shear strains, and the local bonding configurations. The cation alloying plays a crucial role especially for the arsenic nuclei. The isotopic line profiles also largely differ among nuclear species: While the central transition of the gallium isotopes have a narrow linewidth, those of arsenic and indium are much broader and oppositely skewed with respect to each other. The statistical distributions of electric field gradient (EFG) parameters of the nuclei within the QD are analyzed. The consequences of various EFG axial orientation characteristics are discussed. Finally, the possibility of suppressing the first-order quadrupolar shifts is demonstrated by simply tilting the sample with respect to the static magnetic field. © 2014 American Physical Society

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Section: Introductionmentioning

confidence: 99%

Nuclear magnetic resonance inverse spectra of InGaAs quantum dots: Atomistic level structural information

2014

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“…The success of this technology will rely on our ability to understand and control more and more intricate quantum states and their evolution. One of the main challenges is to control the interaction of a quantum system with its environment [1][2][3]. Such an interaction is detrimental for a quantum application as it leads to the major issue of decoherence.…”

Section: Introductionmentioning

confidence: 99%

Coherent backaction between spins and an electronic bath: Non-Markovian dynamics and low-temperature quantum thermodynamic electron cooling

et al. 2019

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We provide a general analytical framework for calculating the dynamics of a spin system in contact with a bath beyond the Markov approximation. The approach is based on a systematic expansion of the Nakashima-Zwanzig master equation in the weak-coupling limit but makes no assumption on the time dynamics and includes all quantum coherent memory effects leading to non-Markovian dynamics. Our results describe, for the free induction decay, the full time range from the non-Markovian dynamics at short times, to the well-known exponential thermal decay at long times. We provide full analytic results for the entire time range using a bath of itinerant electrons as an archetype for universal quantum fluctuations. Furthermore, we propose a quantum thermodynamic scheme to employ the temperature insensitivity of the non-Markovian decay to transport heat out of the electron system and thus, by repeated re-initialisation of a cluster of spins, to efficiently cool the electrons at very low temperatures.

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“…19). Several papers have discussed nuclear polarization with anomalous direction, but under conditions that do not apply to our experiment [20][21][22][23][24]. The line shift and narrowing occurs at low power, when γ e B 1 FWHM, and the resonance is measured through counting single-shot electron spin readout events.…”

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confidence: 99%

Coherent Control of a SingleSi29Nuclear Spin Qubit

et al. 2014

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Magnetic fluctuations caused by the nuclear spins of a host crystal are often the leading source of decoherence for many types of solid-state spin qubit. In group-IV materials, the spin-bearing nuclei are sufficiently rare that it is possible to identify and control individual host nuclear spins. This work presents the first experimental detection and manipulation of a single 29 Si nuclear spin. The quantum non-demolition (QND) single-shot readout of the spin is demonstrated, and a Hahn echo measurement reveals a coherence time of T2 = 6.3(7) ms -in excellent agreement with bulk experiments. Atomistic modeling combined with extracted experimental parameters provides possible lattice sites for the 29 Si atom under investigation. These results demonstrate that single 29 Si nuclear spins could serve as a valuable resource in a silicon spin-based quantum computer.The presence of non-zero nuclear spins in a host crystal lattice is known to induce decoherence in a central spin qubit through mechanisms such as spectral diffusion [1]. This "nuclear bath" is the primary source of decoherence for 31 P electron and nuclear spin qubits in silicon [2,3], nitrogen-vacancy (NV) centers in diamond [4], as well as for GaAs-based quantum dot spin qubits [5,6]. However, for semiconductors composed of majority spin-zero isotopes (such as silicon and carbon), the low abundance of spin-carrying nuclei allows to resolve the hyperfine couplings of individual nuclei with a central electronic spin, permitting the detection and manipulation of single nuclear spins. This has led to the demonstration of a quantum register for the spin of a NV center in diamond, where the electronic spin state can be stored in individual nuclei [7] and read out in single shot [8]. Quantum error correction protocols have been implemented within these nuclear spin registers [9,10], showing their potential to implement surface-code based quantum computing architectures [11]. Natural silicon contains a 4.7% abundance of the spin-carrying (I = 1/2) 29 Si isotope which, in combination with a localized electron spin, could in principle be used as quantum register or ancilla qubit equivalently to 13 C in NV-diamond. In addition, the 29 Si nuclear spin has itself been championed as a quantum bit in an "allsilicon" quantum computer [12,13].Here we present the first experimental demonstration of single-shot readout, coherent control, and measurement of the coherence properties of an individual 29 Si nuclear spin in natural Si. All measurements were performed with a magnetic field B 0 = 1.77 T, in a dilution refrigerator with electron temperature T el ≈ 250 mK. This work follows from previous experiments where the electron [2] and nuclear [3] spins of a single 31 P donor were detected using a compact nanoscale device [14] consisting of ion-implanted phosphorus donors [15], tunnel-coupled to a silicon MOS single- electron transistor (SET) [16]. Spin control was achieved through microwave and RF excitations generated by an arXiv:1408.1347v1 [cond-mat.mes-hall]

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General theory of feedback control of a nuclear spin ensemble in quantum dots

Cited by 29 publications

References 106 publications

Nuclear magnetic resonance inverse spectra of InGaAs quantum dots: Atomistic level structural information

Nuclear magnetic resonance inverse spectra of InGaAs quantum dots: Atomistic level structural information

Coherent backaction between spins and an electronic bath: Non-Markovian dynamics and low-temperature quantum thermodynamic electron cooling

Coherent Control of a SingleSi29Nuclear Spin Qubit

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