Gate-based high fidelity spin readout in a CMOS device

Urdampilleta, Matias; Niegemann, David J.; Chanrion, Emmanuel; Jadot, Baptiste; Spence, Cameron; Mortemousque, Pierre-André; Bäuerle, Christopher; Hutin, Louis; Bertrand, Benoît; Barraud, S.; Maurand, Romain; Sanquer, M.; Jehl, X.; Franceschi, S. De; Vinet, M.; Meunier, Tristan

doi:10.1038/s41565-019-0443-9

Cited by 127 publications

(99 citation statements)

References 37 publications

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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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confidence: 57%

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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confidence: 57%

Gate-based single-shot readout of spins in silicon

et al. 2019

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“…the applied voltage (i.e. a quantum capacitance), allowing for a dispersive readout by coupling to a detector circuit which can be integrated in the gate chip [10][11][12][13] .…”

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confidence: 99%

“…We can detect the charge in the QD via dispersive [10][11][12][13] by incorporating a tank-circuit (often superconducting) resonator (typically with frequency ω r of a few hundred MHz to a few GHz) into the gate wire and accumulated QD [e.g., Fig. 1(a)], and then sending and reflecting resonant microwaves to it.…”

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confidence: 99%

Induced quantum dot probe for material characterization

Shim

Ruskov

Hurst

et al. 2019

Applied Physics Letters

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We propose a non-destructive means of characterizing a semiconductor wafer via measuring parameters of an induced quantum dot on the material system of interest with a separate probe chip that can also house the measurement circuitry. We show that a single wire can create the dot, determine if an electron is present, and be used to measure critical device parameters. Adding more wires enables more complicated (potentially multi-dot) systems and measurements. As one application for this concept we consider silicon metal-oxidesemiconductor and silicon/silicon-germanium quantum dot qubits relevant to quantum computing and show how to measure low-lying excited states (so-called "valley" states). This approach provides an alternative method for characterization of parameters that are critical for various semiconductor-based quantum dot devices without fabricating such devices.Semiconductor heterostructures often serve as the substrate for many solid-state devices. For quantum devices such as qubits, their quality depends crucially on the properties of these wafers. Often, these qubit characterization parameters can only be ascertained by fabricating the device and measuring it at cryogenic temperatures. Quantum dots (QDs) in silicon for quantum computing (QC) 1 are a great example. The indirect band-gap of silicon creates low-lying excited (valley) states in the QD heterostructure; if the "valley splitting" is too small, initialization, readout and even gate operation of the qubits is impeded. Optimizing the valley splitting of silicon QD qubits-in addition to other important parameters such as coherence time, charge noise, etc.-is needed for the eventual construction of quantum computers, and is limited by the design-fabrication-test cycle time.We propose a method of characterizing material properties using a separate probe chip that both creates the dot(s) and measures them. This concept was inspired by the ion trap stylus approach 2,3 where an ion qubit is trapped on a stylus-like tip that can be brought close to a material to characterize its properties, and also by the scanning nitrogen-vacancy (NV) center tip which can be used to detect magnetic fields at nanoscale for imaging or couple to spin qubits 4 . While these ideas involve putting a qubit on the scanning tip itself, our scheme uses a separate gate chip to induce a qubit in the material structure under study, then measure those material and qubit parameters of interest using the circuits on the gate chip. Indeed, scanning tunneling microscope (STM) tips have already been used to create effective dots on the surface of InAs 5,6 and, more recently, Si 7 , using tunneling to do spectroscopy. Nondestructive characterization of embedded donor atoms in a semiconductor has also been demonstrated using a scanning tip architecture 8,9 . Here, we induce the dot qubit within the material in an environment realistic to quantum computing and consider a) Electronic

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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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Gate-based high fidelity spin readout in a CMOS device

Cited by 127 publications

References 37 publications

Gate-based single-shot readout of spins in silicon

Gate-based single-shot readout of spins in silicon

Induced quantum dot probe for material characterization

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

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