103 research outputs found
A Reconfigurable Gate Architecture for Si/SiGe Quantum Dots
We demonstrate a reconfigurable quantum dot gate architecture that
incorporates two interchangeable transport channels. One channel is used to
form quantum dots and the other is used for charge sensing. The quantum dot
transport channel can support either a single or a double quantum dot. We
demonstrate few-electron occupation in a single quantum dot and extract
charging energies as large as 6.6 meV. Magnetospectroscopy is used to measure
valley splittings in the range of 35-70 microeV. By energizing two additional
gates we form a few-electron double quantum dot and demonstrate tunable tunnel
coupling at the (1,0) to (0,1) interdot charge transition.Comment: Related papers at http://pettagroup.princeton.ed
Microwave spectroscopy on a double quantum dot with an on-chip Josephson oscillator
We present measurements on microwave spectroscopy on a double quantum dot
with an on-chip microwave source. The quantum dots are realized in the
two-dimensional electron gas of an AlGaAs/GaAs heterostructure and are weakly
coupled in series by a tunnelling barrier forming an 'ionic' molecular state.
We employ a Josephson oscillator formed by a long Nb/Al-AlO/Nb junction as
a microwave source. We find photon-assisted tunnelling sidebands induced by the
Josephson oscillator, and compare the results with those obtained using an
externally operated microwave source.Comment: 6 pages, 4 figure
Capacitive crosstalk in gate-based dispersive sensing of spin qubits
In gate-based dispersive sensing, the response of a resonator attached to a
quantum dot gate is detected by a reflected radio-frequency signal. This
enables fast readout of spin qubits and tune up of arrays of quantum dots, but
comes at the expense of increased susceptibility to crosstalk, as the resonator
can amplify spurious signals and induce fluctuations in the quantum dot
potential. We attach tank circuits with superconducting NbN inductors and
internal quality factors >1000 to the interdot barrier gate of
silicon double quantum dot devices. Measuring the interdot transition in
transport, we quantify radio-frequency crosstalk that results in a ring-up of
the resonator when neighbouring plunger gates are driven with frequency
components matching the resonator frequency. This effect complicates qubit
operation and scales with the loaded quality factor of the resonator, the
mutual capacitance between device gate electrodes, and with the inverse of the
parasitic capacitance to ground. Setting qubit frequencies below the resonator
frequency is expected to substantially suppress this type of crosstalk.Comment: 7 pages, 4 figures, supplementary informatio
Single-hole tunneling through a two-dimensional hole gas in intrinsic silicon
In this letter we report single-hole tunneling through a quantum dot in a
two-dimensional hole gas, situated in a narrow-channel field-effect transistor
in intrinsic silicon. Two layers of aluminum gate electrodes are defined on
Si/SiO using electron-beam lithography. Fabrication and subsequent
electrical characterization of different devices yield reproducible results,
such as typical MOSFET turn-on and pinch-off characteristics. Additionally,
linear transport measurements at 4 K result in regularly spaced Coulomb
oscillations, corresponding to single-hole tunneling through individual Coulomb
islands. These Coulomb peaks are visible over a broad range in gate voltage,
indicating very stable device operation. Energy spectroscopy measurements show
closed Coulomb diamonds with single-hole charging energies of 5--10 meV, and
lines of increased conductance as a result of resonant tunneling through
additional available hole states.Comment: 4 pages, 4 figures. This article has been submitted to Applied
Physics Letter
High-order cumulants in the counting statistics of asymmetric quantum dots
Measurements of single electron tunneling through a quantum dot using a
quantum point contact as charge detector have been performed for very long time
traces with very large event counts. This large statistical basis is used for a
detailed examination of the counting statistics for varying symmetry of the
quantum dot system. From the measured statistics we extract high order
cumulants describing the distribution. Oscillations of the high order cumulants
are observed when varying the symmetry. We compare this behavior to the
observed oscillation in time dependence and show that the variation of both
system variables lead to the same kind of oscillating response.Comment: 3 page
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