The Radio-Frequency Single-Electron Transistor (RF-SET): A Fast and Ultrasensitive Electrometer

Schoelkopf, R. J.; Wahlgren, Paula; Кожевников, А. А.; Delsing, Per; Prober, D. E.

doi:10.1126/science.280.5367.1238

Cited by 741 publications

(653 citation statements)

References 20 publications

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“…To detect the quantum capacitance signal we couple the double quantum dot to a resonant circuit which we measure using rf reflectometry [8]. A schematic of the measurement circuit is shown in Fig.…”

Section: Pacs Numbersmentioning

confidence: 99%

Charge and Spin State Readout of a Double Quantum Dot Coupled to a Resonator

et al. 2010

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State readout is a key requirement for a quantum computer. For semiconductor-based qubit devices it is usually accomplished using a separate mesoscopic electrometer. Here we demonstrate a simple detection scheme in which a radio-frequency resonant circuit coupled to a semiconductor double quantum dot is used to probe its charge and spin states. These results demonstrate a new non-invasive technique for measuring charge and spin states in quantum dot systems without requiring a separate mesoscopic detector. PACS numbers:State readout is a key requirement for a quantum information processor. For semiconductor-based qubit devices this is usually accomplished using a separate mesoscopic electrometer such as a quantum point contact (QPC) [1]. Non-invasive detection using a QPC has been critical to recent advances in coherent control of few-electron double quantum dots [2], allowing their charge configurations to be mapped in regimes where transport through the double dot itself is not measurable [3]. Furthermore, through spin-to-charge conversion techniques, spin state measurements of single and double dots have been demonstrated using QPCs [4,5].Resonant microwave circuits have played an important role in performing sensitive measurements of mesoscopic devices. In the case of superconducting charge qubits, earlier schemes used a proximal single electron transistor (SET) charge detector to perform state readout [6,7]. This SET was coupled to an impedance matching rf resonant circuit to form an rf-SET which had dramatically improved sensitivity and bandwidth [8]. Similarly, an rf-QPC has also been realised for broadband charge detection of semiconductor quantum dot devices [9,10].More recently, state readout of a superconducting charge qubit has been accomplished by directly coupling it to a microwave resonant circuit [11][12][13]. Working in the dispersive regime where the resonator and qubit bandgap energies are detuned, the qubit has a state-dependent 'quantum capacitance' which causes a shift in the resonator frequency [14]. This frequency shift can then be detected using standard homodyne detection techniques.In this Letter, we demonstrate dispersive detection using a resonant circuit coupled directly to an AlGaAs/GaAs few-electron double quantum dot device. This allows us to probe the charge state of a single electron confined to a double quantum dot. We also perform a spin-state measurement for a pair of electrons using the resonant circuit. These results demonstrate a new and non-invasive technique for measuring charge and spin states in semiconductor quantum dot systems without the need for a separate mesoscopic detector.In using the resonator to probe the state of a double quantum dot we consider the double dot as a charge qubit where a single electron occupies either the ground state of one dot or the other [16]. The Hamiltonian for this two level system is given by H = 1 2 σ z + tσ x , where is the detuning between the two dot chemical potential energies and t is the interdot tunnel coupling energy which m...

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Section: Pacs Numbersmentioning

confidence: 99%

Charge and Spin State Readout of a Double Quantum Dot Coupled to a Resonator

et al. 2010

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“…(7) which in turn causes σ 1 and 1/Q qp to decrease. interdigitated capacitor with capacitance C ≈ 150 fF and a meandering inductor with inductance L ≈ 3.5 nH, similar to resonators used for reading out single-electron transistors 40 and for circuit QED read-out of qubits 41 . To build the device, a 215 nm Al layer was thermallyevaporated onto a sapphire chip, patterned using optical lithography and wet etched.…”

Section: Loss From Nonequilibrium Distribution Of Quasiparticlesmentioning

confidence: 99%

Effects of nonequilibrium quasiparticles in a thin-film superconducting microwave resonator under optical illumination

et al. 2016

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We have illuminated a thin-film superconducting Al lumped-element microwave resonator with 780 nm light and observed the resonator quality factor and resonance frequency as a function of illumination and microwave power in the 20 to 300 mK temperature range. The optically-induced microwave loss increases with increasing illumination but decreases with increasing microwave power. Although this behavior may suggest the presence of optically activated two-level systems, we find that the loss is better explained by the presence of nonequilibrium quasiparticles generated by the illumination and excited by the microwave drive. We model the system by assuming that the illumination creates an effective source of phonons with energy higher than double the superconducting gap and solve the coupled quasiparticle-phonon rate equations. We fit the simulation results to our measurements and find good agreement with the observed dependence of the resonator quality factor and frequency shift on temperature, microwave power, and optical illumination. Examination of the model reveals approaches to reducing optically-induced loss and improving the relaxation time of superconducting quantum devices.

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“…Other requirements are, the read out electronics should not suffer from charge offset problem, and should be stable against long term operation. High sensitivity and wide bandwidth can be realized using the demonstrated Radio Frequency Single Electron Transistor (RF-SET) based on Al SET [2]. Other conditions have already been realized by the SOI based Silicon SET [3][4][5].…”

Section: Introductionmentioning

confidence: 99%