225 research outputs found
Pseudo-digital quantum bits
Quantum computers are analog devices; thus they are highly susceptible to
accumulative errors arising from classical control electronics. Fast
operation--as necessitated by decoherence--makes gating errors very likely. In
most current designs for scalable quantum computers it is not possible to
satisfy both the requirements of low decoherence errors and low gating errors.
Here we introduce a hardware-based technique for pseudo-digital gate operation.
We perform self-consistent simulations of semiconductor quantum dots, finding
that pseudo-digital techniques reduce operational error rates by more than two
orders of magnitude, thus facilitating fast operation.Comment: 4 pages, 3 figure
Is parking in europe ready for dynamic pricing? A reality check for the private sector
Both Revenue Management (RM) and Dynamic Pricing (DP) are common practices in many industries-e.g., airlines and hotels-but they are still relatively unknown in the parking sector. In Europe, with the exception of for airport parking and in some pilot tests, DP is rarely used by private parking operators or local authorities. The main objective of this conceptual paper is to set an agenda for introducing DP in the private parking sector at a larger scale. After a short review of the existing academic and gray literature, we describe the requirements and instruments that parking companies need to make use of RM. Next, we shortly report on the major existing and/or planned DP parking schemes in Europe. We continue by providing a comprehensive reality check discussing the major challenges the sector faces to apply DP. We conclude by suggesting a road map for private parking operators to successfully implement RM and DP. Finally, we give some indications for future research
Efficient multiqubit entanglement via a spin-bus
We propose an experimentally feasible architecture with controllable
long-range couplings built up from local exchange interactions. The scheme
consists of a spin-bus, with strong, always-on interactions, coupled
dynamically to external qubits of the Loss and DiVincenzo type. Long-range
correlations are enabled by a spectral gap occurring in a finite-size chain.
The bus can also form a hub for multiqubit entangling operations. We show how
multiqubit gates may be used to efficiently generate -states (an important
entanglement resource). The spin-bus therefore provides a route for scalable
solid-state quantum computation, using currently available experimental
resources.Comment: Published versio
Spin Readout and Initialization in a Semiconductor Quantum Dot
Electron spin qubits in semiconductors are attractive from the viewpoint of
long coherence times. However, single spin measurement is challenging. Several
promising schemes incorporate ancillary tunnel couplings that may provide
unwanted channels for decoherence. Here, we propose a novel spin-charge
transduction scheme, converting spin information to orbital information within
a single quantum dot by microwave excitation. The same quantum dot can be used
for rapid initialization, gating, and readout. We present detailed modeling of
such a device in silicon to confirm its feasibility.Comment: Published versio
Sensitivity of quantum gate fidelity to laser phase and intensity noise
The fidelity of gate operations on neutral atom qubits is often limited by
fluctuations of the laser drive. Here, we quantify the sensitivity of quantum
gate fidelities to laser phase and intensity noise. We first develop models to
identify features observed in laser self-heterodyne noise spectra, focusing on
the effects of white noise and servo bumps. In the weak-noise regime,
characteristic of well-stabilized lasers, we show that an analytical theory
based on a perturbative solution of a master equation agrees very well with
numerical simulations that incorporate phase noise. We compute quantum gate
fidelities for one- and two-photon Rabi oscillations and show that they can be
enhanced by an appropriate choice of Rabi frequency relative to spectral noise
peaks. We also analyze the influence of intensity noise with spectral support
smaller than the Rabi frequency. Our results establish requirements on laser
noise levels needed to achieve desired gate fidelities.Comment: v3: added analysis of the Lambda configuratio
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