A Charge Parity Ammeter

Lambert, Nicholas J.; Edwards, Megan; Ciccarelli, Chiara; Ferguson, A. J.

doi:10.1021/nl403659x

Cited by 4 publications

(5 citation statements)

References 32 publications

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“…Analogously to the magnitude response, we observe this phase shift Df at the edges of the conductive regions demonstrating dispersive readout of the charge state of a few-electron quantum dot system. Phase changes of the order of 1 mrad are easily resolved, translating into capacitance detection of B1 aF, smaller than the BfF quantum capacitance of strongly coupled quantum systems 25 . NATURE COMMUNICATIONS | DOI: 10.1038/ncomms7084 ARTICLE Experimental charge sensitivity.…”

Section: Resultsmentioning

confidence: 99%

“…While the high-frequency polarizability of quantum systems is well understood in terms of Sisyphus resistance 22 , and statedependent quantum or tunnelling capacitance [22][23][24][25] , the sensitivity of gate detection has only been reported at the me Hz À 1/2 range for GaAs 19,26 . In other semiconductor materials, charge and spin readout have been achieved [27][28][29][30][31][32] and fast detectors have been demonstrated [33][34][35] but little progress has been made towards gate-based sensing 36 .…”

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confidence: 99%

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Probing the limits of gate-based charge sensing

et al. 2015

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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 me Hz À 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.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

Probing the limits of gate-based charge sensing

et al. 2015

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“…1(d), consists of L, the circuit losses R d and the variable capacitor C 0 = C p + C d placed in parallel and coupled to the line by C c . R d represents dielectric losses in the device and the PCB, and can contain dissipative terms arising from Sisyphus processes [21,26,27,34]. The parasitic capacitance, C p , combines contributions from the device and the PCB.…”

Section: Device and Resonatormentioning

confidence: 99%

Radio-Frequency Capacitive Gate-Based Sensing

et al. 2018

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Developing fast, accurate and scalable techniques for quantum state readout is an active area in semiconductor-based quantum computing. Here, we present results on dispersive sensing of silicon corner state quantum dots coupled to lumped-element electrical resonators via the gate. The gate capacitance of the quantum device is configured in parallel with a superconducting spiral inductor resulting in resonators with loaded Q-factors in the 400-800 range. For a resonator operating at 330 MHz, we achieve a charge sensitivity of 7.7 µe/ √ Hz and, when operating at 616 MHz, we get 1.3 µe/ √ Hz. We perform a parametric study of the resonator to reveal its optimal operation points and perform a circuit analysis to determine the best resonator design. The results place gate-based sensing at par with the best reported radio-frequency single-electron transistor sensitivities while providing a fast and compact method for quantum state readout.

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“…The SDD pattern is defined by electron beam lithography, the metal deposited by multiple-angle thermal evaporation and the tunnel barriers formed by controlled in situ oxidation. In previous work we characterized the normal state behavior of similar devices [20], but here we focus on properties arising from superconductivity.We measure the amplitude and phase of a low power (−121 dBm) radio-frequency signal reflected from a lumped element resonant circuit which, along with the SDD, is maintained at the base temperature of a dilution refrigerator [ Fig. 1(b)].…”

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confidence: 99%

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confidence: 99%

Experimental observation of the breaking and recombination of single Cooper pairs

et al. 2014

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We observe the real-time breaking of single Cooper pairs by monitoring the radio-frequency impedance of a superconducting double quantum dot. The Cooper pair breaking rate in the microscale islands of our device decreases as temperature is reduced, saturating at 2 kHz for temperatures beneath 100 mK. In addition, we measure in real time the quasiparticle recombination into Cooper pairs. Analysis of the recombination rates shows that, in contrast to bulk films, a multistage recombination pathway is followed. Unpaired electronic excitations-quasiparticles-play an important role in determining the behavior of superconducting electrical devices. They lead to even-odd parity effects in Coulomb blockade nanostructures [1,2]; they act as a source of decoherence in superconducting qubits [3]; they cause generation-recombination noise in superconducting resonators [4]; they may be important in superconductingnormal devices for Majorana fermionics [5]; and, importantly, they enable the detection of far-infrared light, for example, in kinetic inductance detectors [6]. In this Rapid Communication we investigate the generation and recombination of single quasiparticle pairs in a superconducting double dot (SDD), a Coulomb blockade nanostructure. Double quantum dots have been widely investigated in the context of semiconducting spin qubits where they enable electrostatic control and measurement over electron spins and spin pairs [7]. Previously, semiconductor double dots have been integrated with superconducting leads, allowing electrostatically tunable supercurrents [8] and the splitting of Cooper pair currents into spatially separated and correlated electron currents [9][10][11]. However, apart from an early study investigating the superconducting double quantum dot as a qubit architecture [12], there have been few studies of this system, thus motivating our current work.We investigate the quasiparticle dynamics in the SDD, therefore, our results are relevant to the long-standing quasiparticle poisoning problem in superconducting qubits [13,14]. It has long been known that incoherent quasiparticle tunneling interrupts the coherent tunneling of Cooper pairs. Quasiparticle poisoning is hence a serious issue in charge-based * ajf1006@cam.ac.uk superconducting qubits [15] and has recently been shown to be relevant in the case of low-charging energy transmon qubits [16]. Experiments on superconducting qubits have shown that by taking extreme care over filtering infrared radiation it is possible to extend coherence times, presumably because of the lower quasiparticle temperatures achieved [17]. Quasiparticle tunneling into a Cooper pair box has been used to detect far-infrared radiation from a blackbody source with a noise-equivalent power of less than 10 −19 W/Hz 1/2 , potentially providing a successor technology to kinetic inductance detectors [18]. In parallel, studies on superconducting resonators have shown a saturation of the quasiparticle population at a relatively high temperature of 140 mK [19]. It remains an experimenta...

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A Charge Parity Ammeter

Cited by 4 publications

References 32 publications

Probing the limits of gate-based charge sensing

Probing the limits of gate-based charge sensing

Radio-Frequency Capacitive Gate-Based Sensing

Experimental observation of the breaking and recombination of single Cooper pairs

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