1
|
Gillard G, Clarke E, Chekhovich EA. Harnessing many-body spin environment for long coherence storage and high-fidelity single-shot qubit readout. Nat Commun 2022; 13:4048. [PMID: 35831368 PMCID: PMC9279416 DOI: 10.1038/s41467-022-31618-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 06/23/2022] [Indexed: 11/09/2022] Open
Abstract
There is a growing interest in hybrid solid-state quantum systems where nuclear spins, interfaced to the electron spin qubit, are used as quantum memory or qubit register. These approaches require long nuclear spin coherence, which until now seemed impossible owing to the disruptive effect of the electron spin. Here we study InGaAs semiconductor quantum dots, demonstrating millisecond-long collective nuclear spin coherence even under inhomogeneous coupling to the electron central spin. We show that the underlying decoherence mechanism is spectral diffusion induced by a fluctuating electron spin. These results provide new understanding of the many-body coherence in central spin systems, required for development of electron-nuclear spin qubits. As a demonstration, we implement a conditional gate that encodes electron spin state onto collective nuclear spin coherence, and use it for a single-shot readout of the electron spin qubit with >99% fidelity.
Collapse
Affiliation(s)
- George Gillard
- Department of Physics and Astronomy, University of Sheffield, Sheffield, S3 7RH, UK.
| | - Edmund Clarke
- Department of Electronic and Electrical Engineering, University of Sheffield, Sheffield, S1 3JD, UK
| | - Evgeny A Chekhovich
- Department of Physics and Astronomy, University of Sheffield, Sheffield, S3 7RH, UK.
| |
Collapse
|
2
|
Denning EV, Gangloff DA, Atatüre M, Mørk J, Le Gall C. Collective Quantum Memory Activated by a Driven Central Spin. PHYSICAL REVIEW LETTERS 2019; 123:140502. [PMID: 31702196 DOI: 10.1103/physrevlett.123.140502] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Indexed: 05/25/2023]
Abstract
Coupling a qubit coherently to an ensemble is the basis for collective quantum memories. A single driven electron in a quantum dot can deterministically excite low-energy collective modes of a nuclear spin ensemble in the presence of lattice strain. We propose to gate a quantum state transfer between this central electron and these low-energy excitations-spin waves-in the presence of a strong magnetic field, where the nuclear coherence time is long. We develop a microscopic theory capable of calculating the exact time evolution of the strained electron-nuclear system. With this, we evaluate the operation of quantum state storage and show that fidelities up to 90% can be reached with a modest nuclear polarization of only 50%. These findings demonstrate that strain-enabled nuclear spin waves are a highly suitable candidate for quantum memory.
Collapse
Affiliation(s)
- Emil V Denning
- Department of Photonics Engineering, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Dorian A Gangloff
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Mete Atatüre
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Jesper Mørk
- Department of Photonics Engineering, Technical University of Denmark, 2800 Kongens Lyngby, Denmark
| | - Claire Le Gall
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| |
Collapse
|
3
|
Pulse control protocols for preserving coherence in dipolar-coupled nuclear spin baths. Nat Commun 2019; 10:3157. [PMID: 31316057 PMCID: PMC6637143 DOI: 10.1038/s41467-019-11160-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 06/26/2019] [Indexed: 11/13/2022] Open
Abstract
Coherence of solid state spin qubits is limited by decoherence and random fluctuations in the spin bath environment. Here we develop spin bath control sequences which simultaneously suppress the fluctuations arising from intrabath interactions and inhomogeneity. Experiments on neutral self-assembled quantum dots yield up to a five-fold increase in coherence of a bare nuclear spin bath. Numerical simulations agree with experiments and reveal emergent thermodynamic behaviour where fluctuations are ultimately caused by irreversible conversion of coherence into many-body quantum entanglement. Simulations show that for homogeneous spin baths our sequences are efficient with non-ideal control pulses, while inhomogeneous bath coherence is inherently limited even under ideal-pulse control, especially for strongly correlated spin-9/2 baths. These results highlight the limitations of self-assembled quantum dots and advantages of strain-free dots, where our sequences can be used to control the fluctuations of a homogeneous nuclear spin bath and potentially improve electron spin qubit coherence. Fluctuating nuclear spin ensembles are a significant decoherence mechanism for solid-state spin qubits. Here the authors introduce an approach to controlling and extending the coherence of a nuclear spin bath around self-assembled quantum dots and gain insight into the many-body dynamics.
Collapse
|
4
|
Gangloff DA, Éthier-Majcher G, Lang C, Denning EV, Bodey JH, Jackson DM, Clarke E, Hugues M, Le Gall C, Atatüre M. Quantum interface of an electron and a nuclear ensemble. Science 2019; 364:62-66. [DOI: 10.1126/science.aaw2906] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Accepted: 02/08/2019] [Indexed: 11/02/2022]
Abstract
Coherent excitation of an ensemble of quantum objects underpins quantum many-body phenomena and offers the opportunity to realize a memory that stores quantum information. Thus far, a deterministic and coherent interface between a spin qubit and such an ensemble has remained elusive. In this study, we first used an electron to cool the mesoscopic nuclear spin ensemble of a semiconductor quantum dot to the nuclear sideband–resolved regime. We then implemented an all-optical approach to access individual quantized electronic-nuclear spin transitions. Lastly, we performed coherent optical rotations of a single collective nuclear spin excitation—a spin wave. These results constitute the building blocks of a dedicated local memory per quantum-dot spin qubit and promise a solid-state platform for quantum-state engineering of isolated many-body systems.
Collapse
|
5
|
Javadi A, Ding D, Appel MH, Mahmoodian S, Löbl MC, Söllner I, Schott R, Papon C, Pregnolato T, Stobbe S, Midolo L, Schröder T, Wieck AD, Ludwig A, Warburton RJ, Lodahl P. Spin-photon interface and spin-controlled photon switching in a nanobeam waveguide. NATURE NANOTECHNOLOGY 2018; 13:398-403. [PMID: 29556004 DOI: 10.1038/s41565-018-0091-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 02/09/2018] [Indexed: 06/08/2023]
Abstract
The spin of an electron is a promising memory state and qubit. Connecting spin states that are spatially far apart will enable quantum nodes and quantum networks based on the electron spin. Towards this goal, an integrated spin-photon interface would be a major leap forward as it combines the memory capability of a single spin with the efficient transfer of information by photons. Here, we demonstrate such an efficient and optically programmable interface between the spin of an electron in a quantum dot and photons in a nanophotonic waveguide. The spin can be deterministically prepared in the ground state with a fidelity of up to 96%. Subsequently, the system is used to implement a single-spin photonic switch, in which the spin state of the electron directs the flow of photons through the waveguide. The spin-photon interface may enable on-chip photon-photon gates, single-photon transistors and the efficient generation of a photonic cluster state.
Collapse
Affiliation(s)
- Alisa Javadi
- Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark.
| | - Dapeng Ding
- Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
| | | | | | | | - Immo Söllner
- Department of Physics, University of Basel, Basel, Switzerland
| | - Rüdiger Schott
- Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, Bochum, Germany
| | - Camille Papon
- Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
| | | | - Søren Stobbe
- Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
| | - Leonardo Midolo
- Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
| | - Tim Schröder
- Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
| | - Andreas Dirk Wieck
- Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, Bochum, Germany
| | - Arne Ludwig
- Department of Physics, University of Basel, Basel, Switzerland
| | | | - Peter Lodahl
- Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark.
| |
Collapse
|
6
|
Éthier-Majcher G, Gangloff D, Stockill R, Clarke E, Hugues M, Le Gall C, Atatüre M. Improving a Solid-State Qubit through an Engineered Mesoscopic Environment. PHYSICAL REVIEW LETTERS 2017; 119:130503. [PMID: 29341723 DOI: 10.1103/physrevlett.119.130503] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Indexed: 06/07/2023]
Abstract
A controlled quantum system can alter its environment by feedback, leading to reduced-entropy states of the environment and to improved system coherence. Here, using a quantum-dot electron spin as a control and probe, we prepare the quantum-dot nuclei under the feedback of coherent population trapping and observe their evolution from a thermal to a reduced-entropy state, with the immediate consequence of extended qubit coherence. Via Ramsey interferometry on the electron spin, we directly access the nuclear distribution following its preparation and measure the emergence and decay of correlations within the nuclear ensemble. Under optimal feedback, the inhomogeneous dephasing time of the electron, T_{2}^{*}, is extended by an order of magnitude to 39 ns. Our results can be readily exploited in quantum information protocols utilizing spin-photon entanglement and represent a step towards creating quantum many-body states in a mesoscopic nuclear-spin ensemble.
Collapse
Affiliation(s)
- G Éthier-Majcher
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - D Gangloff
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - R Stockill
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - E Clarke
- EPSRC National Centre for III-V Technologies, University of Sheffield, Sheffield S1 3JD, United Kingdom
| | - M Hugues
- Université Côte d'Azur, CNRS, CRHEA, rue Bernard Gregory, 06560 Valbonne, France
| | - C Le Gall
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - M Atatüre
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| |
Collapse
|