Spin-Blockade Spectroscopy of 
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 Quantum Dots

Jones, Aaron M.; Pritchett, Emily; Chen, E.H.; Keating, Tyler; Andrews, Reed W.; Blumoff, Jacob; Lorenzo, L.A. De; Eng, Kevin; Ha, Sieu D.; Kiselev, A. A.; Meenehan, Seán M.; Merkel, Seth; Wright, Jeffrey A.; Edge, L. F.; Ross, Richard S.; Rakher, Matthew T.; Borselli, Matthew; Hunter, A. T.

doi:10.1103/physrevapplied.12.014026

Cited by 39 publications

(26 citation statements)

References 60 publications

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“…Measurement of S 12 was accomplished through spinto-charge conversion and charge sensing, with high SNR (∼9) single-shot discrimination enabled by cryogenic HEMT amplification, as in Ref. 18. Each measurement was individually thresholded to map each result to 0 or 1.…”

Section: Methodsmentioning

confidence: 99%

“…We measure the S 12 quantum number (which distinguishes between |0 and the six other spin states) via spin-to-charge conversion [5,16] and charge-state detection using a dot charge sensor (formed using gates whose leads are visible in the top of Fig. 1a) and associated amplification circuitry [5,18]. We denote P 0 as the projector onto S 12 = 0 and the probability of being found in |0 for a density matrix ρ as Tr(P 0 ρ).…”

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confidence: 99%

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Quantifying error and leakage in an encoded Si/SiGe triple-dot qubit

et al. 2019

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Quantum computation requires qubits that satisfy often-conflicting criteria, including scalable control and long-lasting coherence [1]. One approach to creating a suitable qubit is to operate in an encoded subspace of several physical qubits. Though such encoded qubits may be particularly susceptible to leakage out of their computational subspace, they can be insensitive to certain noise processes [2, 3] and can also allow logical control with a single type of entangling interaction [4] while maintaining favorable features of the underlying physical system. Here we demonstrate a qubit encoded in a subsystem of three coupled electron spins confined in gated, isotopically enhanced silicon quantum dots [4, 5]. Using a modified "blind" randomized benchmarking protocol that determines both computational and leakage errors [6, 7], we show that unitary operations have an average total error of 0.35%, with 0.17% of that coming from leakage driven by interactions with substrate nuclear spins. This demonstration utilizes only the voltage-controlled exchange interaction for qubit manipulation and highlights the operational benefits of encoded subsystems, heralding the realization of high-quality encoded multi-qubit operations [4, 8].Electrons trapped in silicon heterostructures have many attractive features, including very long coherence times in isotopically enriched material [9, 10] and compatibility with standard fabrication techniques. Singlespin qubits have recently demonstrated high-fidelity RFcontrolled single-qubit operations [10, 11] and two-qubit gates using the exchange interaction [12][13][14]. However, using RF signals for single-qubit control requires a large, stable magnetic field and introduces challenges with crosstalk. Fortunately, electron spins are particularly well-suited to forming encoded qubits. Two coupled electron spins can be operated at near-zero magnetic field as a "singlet-triplet" qubit [15,16]. That qubit is insensitive to uniform magnetic field fluctuations but still requires a magnetic field gradient for universal control. Three coupled electrons [17] can form a qubit with a tunable electric dipole moment, which could enhance RF selectivity, or the exchange-only qubit, which can be universally controlled using only the exchange interaction and does not require synchronization of gate operations with a local oscillator. Exchange is highly local and can be accurately controlled with a large on-off ratio using only fast voltage pulses. The combination of these features makes the exchange-only qubit especially attractive b X2

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Section: Methodsmentioning

confidence: 99%

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confidence: 99%

Quantifying error and leakage in an encoded Si/SiGe triple-dot qubit

et al. 2019

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“…Applicability to Si spin qubits. All of the necessary steps for conditional teleportation, including barrier-controlled exchange 23 , and readout and initialization via Pauli spin-blockade 42 , have already been demonstrated in Si quantum dots. In general, we expect teleportation to work even better in Si, where magnetic gradients and noise can be reduced.…”

Section: Methodsmentioning

confidence: 99%

Conditional teleportation of quantum-dot spin states

et al. 2020

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Among the different platforms for quantum information processing, individual electron spins in semiconductor quantum dots stand out for their long coherence times and potential for scalable fabrication. The past years have witnessed substantial progress in the capabilities of spin qubits. However, coupling between distant electron spins, which is required for quantum error correction, presents a challenge, and this goal remains the focus of intense research. Quantum teleportation is a canonical method to transmit qubit states, but it has not been implemented in quantum-dot spin qubits. Here, we present evidence for quantum teleportation of electron spin qubits in semiconductor quantum dots. Although we have not performed quantum state tomography to definitively assess the teleportation fidelity, our data are consistent with conditional teleportation of spin eigenstates, entanglement swapping, and gate teleportation. Such evidence for all-matter spin-state teleportation underscores the capabilities of exchange-coupled spin qubits for quantum-information transfer.

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“…Within this two-dimensional space, we can choose an electron pair whose collective spin S ij = 0, 1 defines the qubit basis. The qubit can then be controlled by exchange and measured by Pauli spin blockade [27,28]. In practice the DFS qubit is controlled by manipulating gate voltages to tune J 12 and J 23 ; since there are five gates per qubit, this can be done in multiple ways.…”

Section: Tqd Qubit Operation and Key Quantities For Spin-photon Couplingmentioning

confidence: 99%

Resonant exchange operation in triple-quantum-dot qubits for spin–photon transduction

Pan

Keating²,

Gyure³

et al. 2020

Quantum Sci. Technol.

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Triple quantum dots (TQDs) are promising semiconductor spin qubits because of their all-electrical control via fast, tunable exchange interactions and immunity to global magnetic fluctuations. These qubits couple to photons in the resonant exchange (RX) regime, when exchange is simultaneously active on both qubit axes. However, most theoretical work has been based on phenomenological Fermi-Hubbard models, which may not fully capture the complexity of the qubit spin-charge states in this regime. Here we investigate exchange in Si/SiGe and GaAs TQDs using full configuration interaction (FCI) calculations which better describe practical device operation. We show that high exchange operation in general, and the RX regime in particular, can differ significantly from simple models, presenting new challenges and opportunities for spin-photon coupling. We highlight the impact of device electrostatics and effective mass on exchange and identify a new operating point (XRX) where strong spin-photon coupling is most likely to occur in Si/SiGe TQDs. Based on our numerical results, we analyze the feasibility of a remote entanglement cavity iSWAP protocol and discuss design pathways for improving fidelity. Our analysis provides insight into the requirements for TQD spin-photon transduction and demonstrates more generally the necessity of accurate modeling of exchange in spin qubits. ‡ Present address:

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Spin-Blockade Spectroscopy of Si / Si - Ge Quantum Dots

Cited by 39 publications

References 60 publications

Quantifying error and leakage in an encoded Si/SiGe triple-dot qubit

Quantifying error and leakage in an encoded Si/SiGe triple-dot qubit

Conditional teleportation of quantum-dot spin states

Resonant exchange operation in triple-quantum-dot qubits for spin–photon transduction

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