Characterization of helical Luttinger liquids in microwave stepped-impedance edge resonators

Gourmelon, Alexandre; Kamata, Hiroshi; Berroir, Jean-Marc; Fève, Gwendal; Plaçais, Bernard; Bocquillon, Erwann

doi:10.1103/physrevresearch.2.043383

Cited by 8 publications

(3 citation statements)

References 53 publications

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“…Moreover, resonators with a higher characteristic impedance, approaching the resistance quantum 25 kΩ, could also be conceived e.g. by using carbon nanotubes [88][89][90] or quantum Hall edge states [91][92][93][94], further enhancing the coupling strength. The latter approach is particularly appealing for our system, because in Ge/SiGe heterostructures well-developed quantum Hall plateaus have been recently observed at magnetic fields below 1 T [95].…”

Section: Strong Spin-photon Couplingmentioning

confidence: 99%

Hole spin qubits in thin curved quantum wells

Bosco¹,

Loss²

2022

Preprint

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Hole spin qubits are frontrunner platforms for scalable quantum computers because of their large spin-orbit interaction which enables ultrafast all-electric qubit control at low power. The fastest spin qubits to date are defined in long quantum dots with two tight confinement directions, when the driving field is aligned to the smooth direction. However, in these systems the lifetime of the qubit is strongly limited by charge noise, a major issue in hole qubits. We propose here a different, scalable qubit design, compatible with planar CMOS technology, where the hole is confined in a curved germanium quantum well surrounded by silicon. This design takes full advantage of the strong spin-orbit interaction of holes, and at the same time suppresses charge noise in a wide range of configurations, enabling highly coherent, ultrafast qubit gates. While here we focus on a Si/Ge/Si curved quantum well, our design is also applicable to different semiconductors. Strikingly, these devices allow for ultrafast operations even in short quantum dots by a transversal electric field. This additional driving mechanism relaxes the demanding design constraints, and opens up a new way to reliably interface spin qubits in a single quantum dot to microwave photons. By considering stateof-the-art high-impedance resonators and realistic qubit designs, we estimate interaction strengths of a few hundreds of MHz, largely exceeding the decay rate of spins and photons. Reaching such a strong coupling regime in hole spin qubits will be a significant step towards high-fidelity entangling operations between distant qubits, as well as fast single-shot readout, and will pave the way towards the implementation of a large-scale semiconducting quantum processor.

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Section: Strong Spin-photon Couplingmentioning

confidence: 99%

Hole spin qubits in thin curved quantum wells

Bosco¹,

Loss²

2022

Preprint

View full text Add to dashboard Cite

show abstract

“…tightly squeezed dots [13], or by increasing the resonators impedance, either in superconducting platforms [83][84][85][86] or in carbon nanotubes [87][88][89] and quantum Hall materials [61,67,90,91], where Z r ≈ 25 kΩ. Also, importantly, γ L is independent of the amplitude of B, but depends quadratically on ω r ; see Eq.…”

mentioning

confidence: 99%

Fully Tunable Longitudinal Spin-Photon Interactions in Si and Ge Quantum Dots

et al. 2022

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Spin qubits in silicon and germanium quantum dots are promising platforms for quantum computing, but entangling spin qubits over micrometer distances remains a critical challenge. Current prototypical architectures maximize transversal interactions between qubits and microwave resonators, where the spin state is flipped by nearly resonant photons. However, these interactions cause backaction on the qubit that yields unavoidable residual qubit-qubit couplings and significantly affects the gate fidelity. Strikingly, residual couplings vanish when spin-photon interactions are longitudinal and photons couple to the phase of the qubit. We show that large and tunable spin-photon interactions emerge naturally in state-of-the-art hole spin qubits and that they change from transversal to longitudinal depending on the magnetic field direction. We propose ways to electrically control and measure these interactions, as well as realistic protocols to implement fast high-fidelity two-qubit entangling gates. These protocols work also at high temperatures, paving the way toward the implementation of large-scale quantum processors.

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“…These interactions are enhanced by modifying the quantum dot, e.g. using lightly strained materials and tightly squeezed dots [13], or by increasing the resonators impedance, either in superconducting platforms [76][77][78][79] or in carbon nanotubes [80][81][82] and quantum Hall materials [55,60,83,84], where Z r ≈ 25 kΩ. Also, importantly, γ γ γ L depends quadratically on the resonator frequency, see Eq.…”

mentioning

confidence: 99%

Fully tunable longitudinal spin-photon interactions in Si and Ge quantum dots

Bosco,

Scarlino,

Klinovaja

et al. 2022

Preprint

View full text Add to dashboard Cite

Spin qubits in silicon and germanium quantum dots are promising platforms for quantum computing, but entangling spin qubits over micrometer distances remains a critical challenge. Current prototypical architectures maximize transversal interactions between qubits and microwave resonators, where the spin state is flipped by nearly resonant photons. However, these interactions cause back-action on the qubit, that yield unavoidable residual qubit-qubit couplings and significantly affect the gate fidelity. Strikingly, residual couplings vanish when spin-photon interactions are longitudinal and photons couple to the phase of the qubit. We show that large longitudinal interactions emerge naturally in state-of-the-art hole spin qubits. These interactions are fully tunable and can be parametrically modulated by external oscillating electric fields. We propose realistic protocols to measure these interactions and to implement fast and high-fidelity two-qubit entangling gates. These protocols work also at high temperatures, paving the way towards the implementation of large-scale quantum processors.

show abstract

Characterization of helical Luttinger liquids in microwave stepped-impedance edge resonators

Cited by 8 publications

References 53 publications

Hole spin qubits in thin curved quantum wells

Hole spin qubits in thin curved quantum wells

Fully Tunable Longitudinal Spin-Photon Interactions in Si and Ge Quantum Dots

Fully tunable longitudinal spin-photon interactions in Si and Ge quantum dots

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