Sensitive charge detection has enabled qubit readout in solid-state systems. Recently, an alternative to the well-established charge detection via on-chip electrometers has emerged, based on $\textit{in situ}$ gate detectors and radio-frequency dispersive readout techniques. This approach promises to facilitate scalability by removing the need for additional device components devoted to sensing. Here, we perform gate-based dispersive readout of an accumulation-mode silicon quantum dot. We observe that the response of an accumulation-mode gate detector is significantly affected by its bias voltage, particularly if this exceeds the threshold for electron accumulation. We discuss and explain these results in light of the competing capacitive contributions to the dispersive response.Sensitive charge detection has enabled qubit readout in solid-state systems. Recently, an alternative to the well-established charge detection via on-chip electrometers has emerged, based on $\textit{in situ}$ gate detectors and radio-frequency dispersive readout techniques. This approach promises to facilitate scalability by removing the need for additional device components devoted to sensing. Here, we perform gate-based dispersive readout of an accumulation-mode silicon quantum dot. We observe that the response of an accumulation-mode gate detector is significantly affected by its bias voltage, particularly if this exceeds the threshold for electron accumulation. We discuss and explain these results in light of the competing capacitive contributions to the dispersive response.

May 23, 201712 citations

Dispersive Readout of a Few-Electron Double Quantum Dot with Fast rf Gate Sensors

James Colless, Alice Mahoney, J. M. Hornibrook +4 more

We report the dispersive charge-state readout of a double quantum dot in the few-electron regime using the in situ gate electrodes as sensitive detectors. We benchmark this gate sensing technique against the well established quantum point contact charge detector and find comparable performance with a bandwidth of $\ensuremath{\sim}10\text{ }\text{ }\mathrm{MHz}$ and an equivalent charge sensitivity of $\ensuremath{\sim}6.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}\text{ }\text{ }e/\sqrt{\mathrm{Hz}}$. Dispersive gate sensing alleviates the burden of separate charge detectors for quantum dot systems and promises to enable readout of qubits in scaled-up arrays.We report the dispersive charge-state readout of a double quantum dot in the few-electron regime using the in situ gate electrodes as sensitive detectors. We benchmark this gate sensing technique against the well established quantum point contact charge detector and find comparable performance with a bandwidth of $\ensuremath{\sim}10\text{ }\text{ }\mathrm{MHz}$ and an equivalent charge sensitivity of $\ensuremath{\sim}6.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}\text{ }\text{ }e/\sqrt{\mathrm{Hz}}$. Dispersive gate sensing alleviates the burden of separate charge detectors for quantum dot systems and promises to enable readout of qubits in scaled-up arrays.

arXiv:1210.4645Physical Review LettersJan 25, 2013211 citations

Radio-Frequency Reflectometry in Silicon-Based Quantum Dots

Y. Y. Liu, Stephan G. J. Philips, Lucas Orona +6 more

Radio-frequency (rf) reflectometry offers a fast and sensitive method for charge sensing and spin readout in gated quantum dots. We focus in this work on the implementation of rf readout in accumulation-mode gate-defined quantum dots, where the large parasitic capacitance poses a challenge. We describe and test two methods for mitigating the effect of the parasitic capacitance, one by on-chip modifications and a second by off-chip changes. We demonstrate that on-chip modifications enable high-performance charge readout in $\mathrm{Si}$ / ${\mathrm{Si}}_{x}$ ${\mathrm{Ge}}_{1\ensuremath{-}x}$ quantum dots, achieving a fidelity of 99.9% for a measurement time of $1\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{s}$.Radio-frequency (rf) reflectometry offers a fast and sensitive method for charge sensing and spin readout in gated quantum dots. We focus in this work on the implementation of rf readout in accumulation-mode gate-defined quantum dots, where the large parasitic capacitance poses a challenge. We describe and test two methods for mitigating the effect of the parasitic capacitance, one by on-chip modifications and a second by off-chip changes. We demonstrate that on-chip modifications enable high-performance charge readout in $\mathrm{Si}$/${\mathrm{Si}}_{x}$${\mathrm{Ge}}_{1\ensuremath{-}x}$ quantum dots, achieving a fidelity of 99.9% for a measurement time of $1\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{s}$.

arXiv:2012.14560Physical Review AppliedJul 23, 202132 citations

Probing the limits of gate-based charge sensing

M. Fernando González-Zalba, Sylvain Barraud, Andrew J. Ferguson +1 more

Quantum computation requires a qubit-specific measurement capability to readout the final state of individual qubits. Promising solid-state architectures use external readout electrometers but these can be replaced by a more compact readout element, an in situ gate sensor. Gate-sensing couples the qubit to a resonant circuit via a gate and probes the qubit’s radiofrequency polarizability. Here we investigate the ultimate performance of such a resonant readout scheme and the noise sources that limit its operation. We find a charge sensitivity of 37 μe Hz−1/2, the best value reported for this technique, using the example of a gate sensor strongly coupled to a double quantum dot at the corner states of a silicon nanowire transistor. We discuss the experimental factors limiting gate detection and highlight ways to optimize its sensitivity. In total, resonant gate-based readout has advantages over external electrometers both in terms of reduction of circuit elements as well as absolute charge sensitivity. Reading out the state of quantum bits is an essential requirement that any quantum computer implementation must satisfy. Gonzalez-Zalba et al. now show that in situresonant gate-based detection can be a more sensitive approach than external electrometers while reducing the qubit architecture’s complexity.Quantum computation requires a qubit-specific measurement capability to readout the final state of individual qubits. Promising solid-state architectures use external readout electrometers but these can be replaced by a more compact readout element, an in situ gate sensor. Gate-sensing couples the qubit to a resonant circuit via a gate and probes the qubit’s radiofrequency polarizability. Here we investigate the ultimate performance of such a resonant readout scheme and the noise sources that limit its operation. We find a charge sensitivity of 37 μe Hz−1/2, the best value reported for this technique, using the example of a gate sensor strongly coupled to a double quantum dot at the corner states of a silicon nanowire transistor. We discuss the experimental factors limiting gate detection and highlight ways to optimize its sensitivity. In total, resonant gate-based readout has advantages over external electrometers both in terms of reduction of circuit elements as well as absolute charge sensitivity. Reading out the state of quantum bits is an essential requirement that any quantum computer implementation must satisfy. Gonzalez-Zalba et al. now show that in situresonant gate-based detection can be a more sensitive approach than external electrometers while reducing the qubit architecture’s complexity.

arXiv:1405.2755Nature CommunicationsJan 20, 2015173 citations

Radio-Frequency Capacitive Gate-Based Sensing

Imtiaz Ahmed, J. A. Haigh, Simon Schaal +8 more

Quantum computation requires a qubit-specific measurement capability to read out the final states of individual qubits. Promising semiconductor architectures use external readout electrometers, but these could be replaced by more scalable $g\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}e$ $s\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}s\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}s$, based on the dispersive coupling between an electrical resonator and the qubit. The authors present an optimized gate sensor and show that significantly better sensitivity arises from changing circuit topology to enhance the resonator's $Q$ factor. Here CMOS-based quantum devices achieve charge sensitivity on par with that of the best single-electron electrometers.Quantum computation requires a qubit-specific measurement capability to read out the final states of individual qubits. Promising semiconductor architectures use external readout electrometers, but these could be replaced by more scalable $g\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}e$ $s\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}s\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}s$, based on the dispersive coupling between an electrical resonator and the qubit. The authors present an optimized gate sensor and show that significantly better sensitivity arises from changing circuit topology to enhance the resonator's $Q$ factor. Here CMOS-based quantum devices achieve charge sensitivity on par with that of the best single-electron electrometers.

arXiv:1801.09759Physical Review AppliedJul 19, 201875 citations

Dispersive vs charge-sensing readout for linear quantum registers

A. Aprá, Alessandro Crippa, M. L. V. Tagliaferri +17 more

We present recent progress in the implementation of scalable schemes for spin qubit readout in one dimensional quantum registers based on fully-depleted silicon-on-insulator (FDSOI) technology. We compare two schemes both based on rf gate reflectometry. The first one, denoted as dispersive readout, minimizes the device overhead thereby facilitating scale-up to large qubit registers. The second one, denoted as charge-sensing readout, requires additional readout components but is less sensitive to the strength of the interdot coupling facilitating operation in the few-electron regime. We demonstrate single-shot charge sensing with a fidelity of 97% in 5 μs. Finally, we propose a scalable device architecture for linear qubit registers relying on charge-sensing readout.We present recent progress in the implementation of scalable schemes for spin qubit readout in one dimensional quantum registers based on fully-depleted silicon-on-insulator (FDSOI) technology. We compare two schemes both based on rf gate reflectometry. The first one, denoted as dispersive readout, minimizes the device overhead thereby facilitating scale-up to large qubit registers. The second one, denoted as charge-sensing readout, requires additional readout components but is less sensitive to the strength of the interdot coupling facilitating operation in the few-electron regime. We demonstrate single-shot charge sensing with a fidelity of 97% in 5 μs. Finally, we propose a scalable device architecture for linear qubit registers relying on charge-sensing readout.

Technical digest - International Electron Devices Meeting/Technical digestDec 12, 20203 citations

Sensitive charge detection has enabled qubit readout in solid-state systems. Recently, an alternative to the well-established charge detection via on-chip electrometers has emerged, based on

\textit{in situ}

gate detectors and radio-frequency dispersive readout techniques. This approach promises to facilitate scalability by removing the need for additional device components devoted to sensing. Here, we perform gate-based dispersive readout of an accumulation-mode silicon quantum dot. We observe that the response of an accumulation-mode gate detector is significantly affected by its bias voltage, particularly if this exceeds the threshold for electron accumulation. We discuss and explain these results in light of the competing capacitive contributions to the dispersive response.

\mathrm{Si}

{\mathrm{Si}}_{x}

${\mathrm{Ge}}_{1\ensuremath{-}x}$ quantum dots, achieving a fidelity of 99.9% for a measurement time of $1\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{s}$.

Q

factor. Here CMOS-based quantum devices achieve charge sensitivity on par with that of the best single-electron electrometers.