2,124 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
Scalable gate architecture for densely packed semiconductor spin qubits
We demonstrate a 12 quantum dot device fabricated on an undoped Si/SiGe
heterostructure as a proof-of-concept for a scalable, linear gate architecture
for semiconductor quantum dots. The device consists of 9 quantum dots in a
linear array and 3 single quantum dot charge sensors. We show reproducible
single quantum dot charging and orbital energies, with standard deviations less
than 20% relative to the mean across the 9 dot array. The single quantum dot
charge sensors have a charge sensitivity of 8.2 x 10^{-4} e/root(Hz) and allow
the investigation of real-time charge dynamics. As a demonstration of the
versatility of this device, we use single-shot readout to measure a spin
relaxation time T1 = 170 ms at a magnetic field B = 1 T. By reconfiguring the
device, we form two capacitively coupled double quantum dots and extract a
mutual charging energy of 200 microeV, which indicates that 50 GHz two-qubit
gate operation speeds are feasible
A Coherent Spin-Photon Interface in Silicon
Electron spins in silicon quantum dots are attractive systems for quantum
computing due to their long coherence times and the promise of rapid scaling
using semiconductor fabrication techniques. While nearest neighbor exchange
coupling of two spins has been demonstrated, the interaction of spins via
microwave frequency photons could enable long distance spin-spin coupling and
"all-to-all" qubit connectivity. Here we demonstrate strong-coupling between a
single spin in silicon and a microwave frequency photon with spin-photon
coupling rates g_s/(2\pi) > 10 MHz. The mechanism enabling coherent spin-photon
interactions is based on spin-charge hybridization in the presence of a
magnetic field gradient. In addition to spin-photon coupling, we demonstrate
coherent control of a single spin in the device and quantum non-demolition spin
state readout using cavity photons. These results open a direct path toward
entangling single spins using microwave frequency photons
Investigation of Mobility Limiting Mechanisms in Undoped Si/SiGe Heterostructures
We perform detailed magnetotransport studies on two-dimensional electron
gases (2DEGs) formed in undoped Si/SiGe heterostructures in order to identify
the electron mobility limiting mechanisms in this increasingly important
materials system. By analyzing data from 26 wafers with different
heterostructure growth profiles we observe a strong correlation between the
background oxygen concentration in the Si quantum well and the maximum
mobility. The highest quality wafer supports a 2DEG with a mobility of 160,000
cm^2/Vs at a density 2.17 x 10^11/cm^2 and exhibits a metal-to-insulator
transition at a critical density 0.46 x 10^11/cm^2. We extract a valley
splitting of approximately 150 microeV at a magnetic field of 1.8 T. These
results provide evidence that undoped Si/SiGe heterostructures are suitable for
the fabrication of few-electron quantum dots.Comment: Related papers at http://pettagroup.princeton.ed
Screening nuclear field fluctuations in quantum dots for indistinguishable photon generation
A semiconductor quantum dot can generate highly coherent and
indistinguishable single photons. However, intrinsic semiconductor dephasing
mechanisms can reduce the visibility of two-photon interference. For an
electron in a quantum dot, a fundamental dephasing process is the hyperfine
interaction with the nuclear spin bath. Here we directly probe the consequence
of the fluctuating nuclear spins on the elastic and inelastic scattered photon
spectra from a resident electron in a single dot. We find the nuclear spin
fluctuations lead to detuned Raman scattered photons which are distinguishable
from both the elastic and incoherent components of the resonance fluorescence.
This significantly reduces two-photon interference visibility. However, we
demonstrate successful screening of the nuclear spin noise which enables the
generation of coherent single photons that exhibit high visibility two-photon
interference.Comment: 5 pages, 4 figures + Supplementary Informatio
Time Evolution of the Radial Perturbations and Linear Stability of Solitons and Black Holes in a Generalized Skyrme Model
We study the time evolution of the radial perturbation for self-gravitating
soliton and black-hole solutions in a generalized Skyrme model in which a
dilaton is present. The background solutions were obtained recently by some of
the authors. For both the solitons and the black holes two branches of
solutions exist which merge at some critical value of the corresponding
parameter. The results show that, similar to the case without a scalar field,
one of the branches is stable against radial perturbations and the other is
unstable. The conclusions for the linear stability of the black holes in the
generalized Skyrme model are also in agreement with the results from the
thermodynamical stability analysis based on the turning point method.Comment: 18 pages, 12 figures; v2: typos corrected, comments adde
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