2,951 research outputs found
Critical Behaviour of the 3d Gross-Neveu and Higgs-Yukawa Models
We measure the critical exponents of the three dimensional Gross-Neveu model
with two four-component fermions. The exponents are inferred from the scaling
behaviour of observables on different lattice sizes. We also calculate the
exponents, through a second order epsilon-expansion around 4d, for the three
dimensional Higgs-Yukawa model, which is expected to be in the same
universality class and we find that the exponents agree. We conclude that the
equivalence of the two models remains valid in 3d at fixed small N_f values.Comment: 14 Latex pages 8 PSfigures included at the
end,BI-TP-93/31,AZPH-TH/93-19,SPhT 93/0
Field Tuning the G-Factor in InAs Nanowire Double Quantum Dots
We study the effects of magnetic and electric fields on the g-factors of
spins confined in a two-electron InAs nanowire double quantum dot. Spin
sensitive measurements are performed by monitoring the leakage current in the
Pauli blockade regime. Rotations of single spins are driven using
electric-dipole spin resonance. The g-factors are extracted from the spin
resonance condition as a function of the magnetic field direction, allowing
determination of the full g-tensor. Electric and magnetic field tuning can be
used to maximize the g-factor difference and in some cases altogether quench
the EDSR response, allowing selective single spin control.Comment: Related papers at http://pettagroup.princeton.ed
Radio frequency charge sensing in InAs nanowire double quantum dots
We demonstrate charge sensing of an InAs nanowire double quantum dot (DQD)
coupled to a radio frequency (rf) circuit. We measure the rf signal reflected
by the resonator using homodyne detection. Clear single dot and DQD behavior
are observed in the resonator response. rf-reflectometry allows measurements of
the DQD charge stability diagram in the few-electron regime even when the dc
current through the device is too small to be measured. For a signal-to-noise
ratio of one, we estimate a minimum charge detection time of 350 microseconds
at interdot charge transitions and 9 microseconds for charge transitions with
the leads.Comment: Related papers at http://pettagroup.princeton.ed
Discontinuity Theorem for First Order Phase Transitions. Implications for QCD
A first order phase transition leading to deconfinement and chiral
restoration is a likely possibility for QCD, at least in some region of the
temperature-density plane. A signal for a unique transition is that the order
parameters for such transitions (which can be understood in terms of symmetries
only in limiting situations of very massive or massless quarks) are both
discontinuous at the same critical temperature. We show that such a situation
can be understood on a precise thermodynamical basis because of a general
relation among discontinuities which holds for first order transitions. We
derive the result by a generalization of the Clausius-Clapeyron equation and
also through the effective action formalism. We illustrate the theorem in an
elementary example.Comment: 10 pages, LATEX, UGVA-DPT 1992/12/79
Nonadiabatic quantum control of a semiconductor charge qubit
We demonstrate multipulse quantum control of a single electron charge qubit.
The qubit is manipulated by applying nonadiabatic voltage pulses to a surface
depletion gate and readout is achieved using a quantum point contact charge
sensor. We observe Ramsey fringes in the excited state occupation in response
to a pi/2 - pi/2 pulse sequence and extract T2* ~ 60 ps away from the charge
degeneracy point. Simulations suggest these results may be extended to
implement a charge-echo by reducing the interdot tunnel coupling and pulse rise
time, thereby increasing the nonadiabaticity of the pulses.Comment: Related papers at http://pettagroup.princeton.ed
Multi-mode photonic crystal fibers for VCSEL based data transmission
Quasi error-free 10 Gbit/s data transmission is demonstrated over a novel
type of 50 micron core diameter photonic crystal fiber with as much as 100 m
length. Combined with 850$ nm VCSEL sources, this fiber is an attractive
alternative to graded-index multi-mode fibers for datacom applications. A
comparison to numerical simulations suggests that the high bit-rate may be
partly explained by inter-modal diffusion.Comment: Accepted for Optics Expres
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