Single-Shot Single-Gate rf Spin Readout in Silicon

Pakkiam, Prasanna; Timofeev, A.; House, Matthew; Hogg, Mark; Kobayashi, Takashi; Koch, Matthias; Rogge, Sven; Simmons, M. Y.

doi:10.1103/physrevx.8.041032

Cited by 88 publications

(72 citation statements)

References 35 publications

(54 reference statements)

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“…In summary, we have characterised a gate-based approach for spin-qubit measurements in a future silicon quantum processor.The signal-to-noise ratio obtained with a simple resonant circuit is sufficient to read out the electronic spin state in a single shot. Our results, together with contemporaneous results in several other silicon quantum dot architectures [31][32][33], open a path to the readout of many spin qubits in parallel, using a compact gate design that will be needed for large-scale quantum processors of the future. SET current (left) and dispersive response (right) measured after initialising either via A1 → A2, to initialise S, or via B1 → B2 to initialise a mixed state between S and the three triplets (pulse sequence is shown in inset).…”

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Gate-based single-shot readout of spins in silicon

et al. 2019

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Electron spins in silicon quantum dots provide a promising route towards realising the large number of coupled qubits required for a useful quantum processor [1][2][3][4][5][6][7][8]. At present, the requisite single-shot spin qubit measurements are performed using on-chip charge sensors, capacitively coupled to the quantum dots. However, as the number of qubits is increased, this approach becomes impractical due to the footprint and complexity of the charge sensors, combined with the required proximity to the quantum dots [5]. Alternatively, the spin state can be measured directly by detecting the complex impedance of spin-dependent electron tunnelling between quantum dots [9][10][11]. This can be achieved using radio-frequency reflectometry on a single gate electrode defining the quantum dot itself [11][12][13][14][15], significantly reducing gate count and architectural complexity, but thus far it has not been possible to achieve single-shot spin readout using this technique. Here, we detect single electron tunnelling in a double quantum dot and demonstrate that gate-based sensing can be used to read out the electron spin state in a single shot, with an average readout fidelity of 73%. The result demonstrates a key step towards the readout of many spin qubits in parallel, using a compact gate design that will be needed for a large-scale semiconductor quantum processor.

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Gate-based single-shot readout of spins in silicon

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“…They ensure that the operators appearing in Eq. (16) are expressed in a basis that is close to the true eigenbasis of the full system Hamiltonian H. If the transition term becomes resonant, the resulting change of basis enables probe photons to generate new transitions between the system eigenstates.…”

Section: A Dispersive Limitmentioning

confidence: 99%

Optimal dispersive readout of a spin qubit with a microwave resonator

D’Anjou

Burkard

2019

Phys. Rev. B

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Strong coupling of semiconductor spin qubits to superconducting microwave resonators was recently demonstrated [X. Mi et al., Nature 555, 599 (2018); A. J. Landig et al., Nature 560, 179 (2018); N. Samkharadze et al., Science 359, 1123 T. Cubaynes et al., npj Quantum Inf. 5, 47 (2019)]. These breakthroughs pave the way for quantum information processing that combines the long coherence times of solid-state spin qubits with the long-distance connectivity, fast control, and fast high-fidelity quantum-non-demolition readout of existing superconducting qubit implementations. Here, we theoretically analyze and optimize the dispersive readout of a single spin in a semiconductor double quantum dot (DQD) coupled to a microwave resonator via its electric dipole moment. The strong spin-photon coupling arises from the motion of the electron spin in a local magnetic field gradient. We calculate the signal-to-noise ratio (SNR) of the readout accounting for both Purcell spin relaxation and spin relaxation arising from intrinsic electric noise within the semiconductor. We express the maximum achievable SNR in terms of the cooperativity associated with these two dissipation processes. We find that while the cooperativity increases with the strength of the dipole coupling between the DQD and the resonator, it does not depend on the strength of the magnetic field gradient. We then optimize the SNR as a function of experimentally tunable DQD parameters. We identify wide regions of parameter space where the unwanted backaction of the resonator photons on the qubit is small. Moreover, we find that the coupling of the resonator to other DQD transitions can enhance the SNR by at least a factor of two, a "straddling" effect [J. Koch et al., Phys. Rev. A 76, 042319 (2007)] that occurs only at nonzero energy detuning of the DQD double-well potential. We estimate that with current technology, single-shot readout fidelities in the range 82 − 95% can be achieved within a few µs of readout time without requiring the use of Purcell filters. arXiv:1905.09702v2 [cond-mat.mes-hall]

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“…1(b), resulting in a large gate-coupling factor, α = 0.95±0.06, similar to previously reported values 11,12 . The results presented in this paper are performed in a cryo-free dilution refrigerator using gate-based reflectometry and homodyne detection [13][14][15][16][17] .For the typically large impedances of nanoelectronic devices at radio-frequencies, the circuit's resonant frequency is f 0 ≈ 1/(2π √ LC tot ) where C tot = C t +C d +C p . The equivalent impedance at resonance is arXiv:1807.07842v2 [cond-mat.mes-hall]…”

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Low-temperature tunable radio-frequency resonator for sensitive dispersive readout of nanoelectronic devices

Ibberson

Smithson

et al. 2019

Applied Physics Letters

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We present a sensitive, tunable radio-frequency resonator designed to detect reactive changes in nanoelectronic devices down to dilution refrigerator temperatures. The resonator incorporates GaAs varicap diodes to allow electrical tuning of the resonant frequency and the coupling to the input line. We find a resonant frequency tuning range of 8.4 MHz at 55 mK that increases to 29 MHz at 1.5 K. To assess the impact on performance of different tuning conditions, we connect a quantum dot in a silicon nanowire field-effect transistor to the resonator, and measure changes in the device capacitance caused by cyclic electron tunneling. At 250 mK, we obtain an equivalent charge sensitivity of 43 µe/ √ Hz when the resonator and the line are impedancematched and show that this sensitivity can be further improved to 31 µe/ √ Hz by re-tuning the resonator. We understand this improvement by using an equivalent circuit model and demonstrate that for maximum sensitivity to capacitance changes, in addition to impedance matching, a high-quality resonator with low parasitic capacitance is desired.High-frequency reflectometry is a technique widely used to study the dynamical properties of nanoelectronic devices due to its enhanced sensitivity and large bandwidth when compared to direct current measurements 1,2 . By embedding a device in an electrical resonator, resistive or reactive changes in the device can be inferred from the resonator's response.Previous work has shown that, for sensitive detection of resistive changes, good impedance matching between the high frequency line and the resonator, as well as large fractional changes in resistance, are paramount 3,4 . Tunable resonators have recently been explored for sensitive capacitance readout 5,6 , concluding that optimal sensitivity occurs when the resonator is impedance matched to the line. In this Letter, we extend the work of Ares et al. and demonstrate that for maximal sensitivity to capacitance changes, in addition to an optimally matched resonator, large fractional changes in capacitance and a high internal-Q resonator are essential. We focus on dispersive changes because, for quantum computing technologies, measurement via detection of reactive changes is preferred since it allows for quantum-limited measurements of the qubits 7-9 .To achieve this, we present a tunable high-frequency resonator that remains operational at the base temperature of a dilution refrigerator and allows matching to be achieved at 200 mK. In previous reports, impedance matching was limited to temperatures of 1 K and above 5,10 . We couple our resonator to a quana) david.ibberson@bristol.ac.uk b) mg507@cam.ac.uk tum dot (QD) in a silicon nanowire field-effect transistor (NWFET) and measure changes in the device capacitance due to adiabatic single-electron tunneling events. We observe that sensitive detection of capacitance changes relies on an optimal balance of maximum power transfer to the resonator, maximal internal quality factor and minimized resonator capacitance, and that all three paramet...

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Single-Shot Single-Gate rf Spin Readout in Silicon

Cited by 88 publications

References 35 publications

Gate-based single-shot readout of spins in silicon

Gate-based single-shot readout of spins in silicon

Optimal dispersive readout of a spin qubit with a microwave resonator

Low-temperature tunable radio-frequency resonator for sensitive dispersive readout of nanoelectronic devices

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