193,913 research outputs found
On the "principle of the quantumness", the quantumness of Relativity, and the computational grand-unification
After reviewing recently suggested operational "principles of the
quantumness", I address the problem on whether Quantum Theory (QT) and Special
Relativity (SR) are unrelated theories, or instead, if the one implies the
other. I show how SR can be indeed derived from causality of QT, within the
computational paradigm "the universe is a huge quantum computer", reformulating
QFT as a Quantum-Computational Field Theory (QCFT). In QCFT SR emerges from the
fabric of the computational network, which also naturally embeds gauge
invariance. In this scheme even the quantization rule and the Planck constant
can in principle be derived as emergent from the underlying causal tapestry of
space-time. In this way QT remains the only theory operating the huge computer
of the universe. Is QCFT only a speculative tautology (theory as simulation of
reality), or does it have a scientific value? The answer will come from Occam's
razor, depending on the mathematical simplicity of QCFT. Here I will just start
scratching the surface of QCFT, analyzing simple field theories, including
Dirac's. The number of problems and unmotivated recipes that plague QFT
strongly motivates us to undertake the QCFT project, since QCFT makes all such
problems manifest, and forces a re-foundation of QFT.Comment: To be published on AIP Proceedings of Vaxjo conference. The ideas on
Quantum-Circuit Field Theory are more recent. V4 Largely improved, with new
interesting results and concepts. Dirac equation solve
Analysis and design of a two-speed single-phase induction motor with 2 and 18 pole special windings
The motor presented employs multiple independent windings for operation with two very different pole numbers. The 18-pole field is produced with a symmetrical three-phase winding connected in a Steinmetz arrangement to a single-phase supply. A unified analysis method has been developed and used to demonstrate the equivalence of a Steinmetz delta or star connection with a main and auxiliary winding of a single-phase motor. The method has been experimentally validated and also included are some specific motor design considerations
Physics as Information Processing
I review some recent advances in foundational research at Pavia QUIT group.
The general idea is that there is only Quantum Theory without quantization
rules, and the whole Physics---including space-time and relativity--is emergent
from the quantum-information processing. And since Quantum Theory itself is
axiomatized solely on informational principles, the whole Physics must be
reformulated in information-theoretical terms: this is the "It from Bit of J.
A. Wheeler. The review is divided into four parts: a) the informational
axiomatization of Quantum Theory; b) how space-time and relativistic covariance
emerge from quantum computation; c) what is the information-theoretical meaning
of inertial mass and of , and how the quantum field emerges; d) an
observational consequence of the new quantum field theory: a mass-dependent
refraction index of vacuum. I will conclude with the research lines that will
follow in the immediate future.Comment: Work presented at the conference "Advances in Quantum Theory" held on
14-17 June 2010 at the Linnaeus University, Vaxjo, Swede
Parametric Macromodels of Differential Drivers and Receivers
This paper addresses the modeling of differential drivers and receivers for the analog simulation of high-speed interconnection systems. The proposed models are based on mathematical expressions, whose parameters can be estimated from the transient responses of the modeled devices. The advantages of this macromodeling approach are: improved accuracy with respect to models based on simplified equivalent circuits of devices; improved numerical efficiency with respect to detailed transistor-level models of devices; hiding of the internal structure of devices; straightforward circuit interpretation; or implementations in analog mixed-signal simulators. The proposed methodology is demonstrated on example devices and is applied to the prediction of transient waveforms and eye diagrams of a typical low-voltage differential signaling (LVDS) data link
Entropy flow in near-critical quantum circuits
Near-critical quantum circuits are ideal physical systems for asymptotically
large-scale quantum computers, because their low energy collective excitations
evolve reversibly, effectively isolated from the environment. The design of
reversible computers is constrained by the laws governing entropy flow within
the computer. In near-critical quantum circuits, entropy flows as a locally
conserved quantum current, obeying circuit laws analogous to the electric
circuit laws. The quantum entropy current is just the energy current divided by
the temperature. A quantum circuit made from a near-critical system (of
conventional type) is described by a relativistic 1+1 dimensional relativistic
quantum field theory on the circuit. The universal properties of the
energy-momentum tensor constrain the entropy flow characteristics of the
circuit components: the entropic conductivity of the quantum wires and the
entropic admittance of the quantum circuit junctions. For example,
near-critical quantum wires are always resistanceless inductors for entropy. A
universal formula is derived for the entropic conductivity:
\sigma_S(\omega)=iv^{2}S/\omega T, where \omega is the frequency, T the
temperature, S the equilibrium entropy density and v the velocity of `light'.
The thermal conductivity is Real(T\sigma_S(\omega))=\pi v^{2}S\delta(\omega).
The thermal Drude weight is, universally, v^{2}S. This gives a way to measure
the entropy density directly.Comment: 2005 paper published 2017 in Kadanoff memorial issue of J Stat Phys
with revisions for clarity following referee's suggestions, arguments and
results unchanged, cross-posting now to quant-ph, 27 page
Exponential Quantum Speed-ups are Generic
A central problem in quantum computation is to understand which quantum
circuits are useful for exponential speed-ups over classical computation. We
address this question in the setting of query complexity and show that for
almost any sufficiently long quantum circuit one can construct a black-box
problem which is solved by the circuit with a constant number of quantum
queries, but which requires exponentially many classical queries, even if the
classical machine has the ability to postselect.
We prove the result in two steps. In the first, we show that almost any
element of an approximate unitary 3-design is useful to solve a certain
black-box problem efficiently. The problem is based on a recent oracle
construction of Aaronson and gives an exponential separation between quantum
and classical bounded-error with postselection query complexities.
In the second step, which may be of independent interest, we prove that
linear-sized random quantum circuits give an approximate unitary 3-design. The
key ingredient in the proof is a technique from quantum many-body theory to
lower bound the spectral gap of local quantum Hamiltonians.Comment: 24 pages. v2 minor correction
Causal structure of the entanglement renormalization ansatz
We show that the multiscale entanglement renormalization ansatz (MERA) can be
reformulated in terms of a causality constraint on discrete quantum dynamics.
This causal structure is that of de Sitter space with a flat spacelike
boundary, where the volume of a spacetime region corresponds to the number of
variational parameters it contains. This result clarifies the nature of the
ansatz, and suggests a generalization to quantum field theory. It also
constitutes an independent justification of the connection between MERA and
hyperbolic geometry which was proposed as a concrete implementation of the
AdS-CFT correspondence
Inertial Load Compensation by a Model Spinal Circuit During Single Joint Movement
Office of Naval Research (N00014-92-J-1309); CONACYT (Mexico) (63462
Recommended from our members
Fast, non-monte-carlo estimation of transient performance variation due to device mismatch
This paper describes an efficient way of simulating the effects of device random mismatch on circuit transient characteristics, such as variations in delay or in frequency. The proposed method models DC random offsets as equivalent AC pseudo-noises and leverages the fast, linear periodically time-varying (LPTV) noise analysis available from RF circuit simulators. Therefore, the method can be considered as an extension to DC match analysis and offers a large speed-up compared to the traditional Monte-Carlo analysis. Although the assumed linear perturbation model is valid only for small variations, it enables easy ways to estimate correlations among variations and identify the most sensitive design parameters to mismatch, all at no additional simulation cost. Three benchmarks measuring the variations in the input offset voltage of a clocked comparator, the delay of a logic path, and the frequency of an oscillator demonstrate the speed improvement of about 100-1000x compared to a 1000-point Monte-Carlo method
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