QuanTELCO

Institutionen
  • AG Burkard (Theoretische Physik mit SP Festkörperphysik und Quanteninformation)
Publikationen
  (2024): Efficient high-fidelity flying qubit shaping Physical Review Research. American Physical Society (APS). 2024, 6(1), 013150. eISSN 2643-1564. Available under: doi: 10.1103/physrevresearch.6.013150

Efficient high-fidelity flying qubit shaping

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Forschungszusammenhang (Projekte)

    Cilibrizzi, Pasquale; Arshad, Muhammad Junaid; Tissot, Benedikt; Son, Nguyen Tien; Ivanov, Ivan G.; Astner, Thomas; Koller, Philipp; Burkard, Guido; Trupke, Michael; Bonato, Cristian (2023): Ultra-narrow inhomogeneous spectral distribution of telecom-wavelength vanadium centres in isotopically-enriched silicon carbide Nature Communications. Springer. 2023, 14(1), 8448. eISSN 2041-1723. Available under: doi: 10.1038/s41467-023-43923-7

Ultra-narrow inhomogeneous spectral distribution of telecom-wavelength vanadium centres in isotopically-enriched silicon carbide

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Spin-active quantum emitters have emerged as a leading platform for quantum technologies. However, one of their major limitations is the large spread in optical emission frequencies, which typically extends over tens of GHz. Here, we investigate single V4+ vanadium centres in 4H-SiC, which feature telecom-wavelength emission and a coherent S  = 1/2 spin state. We perform spectroscopy on single emitters and report the observation of spin-dependent optical transitions, a key requirement for spin-photon interfaces. By engineering the isotopic composition of the SiC matrix, we reduce the inhomogeneous spectral distribution of different emitters down to 100 MHz, significantly smaller than any other single quantum emitter. Additionally, we tailor the dopant concentration to stabilise the telecom-wavelength V4+ charge state, thereby extending its lifetime by at least two orders of magnitude. These results bolster the prospects for single V emitters in SiC as material nodes in scalable telecom quantum networks.

Forschungszusammenhang (Projekte)

  (2023): Optical Spin-Photon Interfaces with a Focus on Transition Metal Defects in Silicon Carbide

Optical Spin-Photon Interfaces with a Focus on Transition Metal Defects in Silicon Carbide

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The conversion between stationary and flying qubits is a pillar of numerous quantum technologies such as distributed quantum computing


as well as many quantum internet and networking protocols.


These quantum technologies promise to use resources, in particular entanglement, not available to classical devices


to accomplish tasks that are difficult or even impossible to realize with classical devices.


Applications range from fundamental research to secure communication.


Because some of these applications require the generation of entanglement, even over large distances,


there is substantial interest in efficient interfaces between flying qubits, usually photons,


and a stationary memory.



In this thesis, we evaluate key aspects of optical spin-photon interfaces,


a class of devices combining a stationary qubit memory (spins) and an interface with flying qubits (photons).


We focus on defects in silicon carbide (SiC) in which a transition metal (TM) atom substitutes a silicon (Si) atom in the lattice,


so that the energy levels with naturally bound quantum states localized around the defect lie within the band gap of SiC.


We highlight two key properties of these defects as stationary-flying interconnects:


First, they have favorable spin coherence properties and the pertaining nuclear spin of the TM can be used as a quantum memory.


Second, they feature a localized and efficient spin-photon interface via their excited states.


Defects where vanadium takes the place of a Si atom even allow for photon emission with frequencies in one of the fiber-optic transmission windows, which support efficient transmission in optical fiber.



Our results are readily combined with numerical ab-initio and experimental data,


providing intuition and further insight into the underlying physics.


Additionally, the theoretical assessments of this thesis bridge the gap between the fundamental characterization of TM defects in SiC


and their use as spin-photon interfaces in future experiments and quantum technology applications.


For instance, the proposed nuclear-spin preparation protocol and spin control


mark the first step towards an all-optically controlled integrated platform for quantum technology with TM defects in SiC.

Forschungszusammenhang (Projekte)

    Tissot, Benedikt; Trupke, Michael; Koller, Philipp; Astner, Thomas; Burkard, Guido (2022): Nuclear Spin Quantum Memory in Silicon Carbide Physical Review Research. American Physical Society. 2022, 4(3), 033107. eISSN 2643-1564. Available under: doi: 10.1103/PhysRevResearch.4.033107

Nuclear Spin Quantum Memory in Silicon Carbide

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Transition metal (TM) defects in silicon carbide (SiC) are a promising platform for applications in quantum technology. Some TM defects, e.g. vanadium, emit in one of the telecom bands, but the large ground state hyperfine manifold poses a problem for applications which require pure quantum states. We develop a driven, dissipative protocol to polarize the nuclear spin, based on a rigorous theoretical model of the defect. We further show that nuclear-spin polarization enables the use of well-known methods for initialization and long-time coherent storage of quantum states. The proposed nuclear-spin preparation protocol thus marks the first step towards an all-optically controlled integrated platform for quantum technology with TM defects in SiC.

Forschungszusammenhang (Projekte)

  (2021): Spin Structure and Resonant Driving of Spin-1/2 Defects in SiC Physical Review B. American Physical Society (APS). 2021, 103(6), 064106. ISSN 2469-9950. eISSN 2469-9969. Available under: doi: 10.1103/PhysRevB.103.064106

Spin Structure and Resonant Driving of Spin-1/2 Defects in SiC

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Transition metal (TM) defects in silicon carbide have favorable spin coherence properties and are suitable as quantum memory for quantum communication. To characterize TM defects as quantum spin-photon interfaces, we model defects that have one active electron with spin 1/2 in the atomic D shell. The spin structure, as well as the magnetic and optical resonance properties of the active electron, emerge from the interplay of the crystal potential and spin-orbit coupling, and they are described by a general model derived using group theory. We find that the spin-orbit coupling leads to additional allowed transitions and a modification of the g-tensor. To describe the dependence of the Rabi frequency on the magnitude and direction of the static and driving fields, we derive an effective Hamiltonian. This theoretical description can also be instrumental in performing and optimizing spin control in TM defects.

Forschungszusammenhang (Projekte)

Mittelgeber
Name Finanzierungstyp Kategorie Kennziffer
ERC Drittmittel Forschungsförderprogramm 843/19
Weitere Informationen
Laufzeit: 01.10.2019 – 30.09.2022