The finite-time operation of a quantum heat engine that uses a single particle as a working medium generally increases the output power at the expense of inducing friction that lowers the cycle efficiency. We propose to scale up a quantum heat engine utilizing a many-particle working medium in combination with the use of shortcuts to adiabaticity to boost the nonadiabatic performance by elimina...

The hypercomputers compute functions that cannot be computed by a Turing machine. Recently, Tien D. Kieu has proposed a hypercomputational quantum algorithm, which uses as physical referent the quantum harmonic oscillator and in principle solves Hilbert’s tenth problem. An analysis of the Kieu’s algorithm is made and it is deduced that the algorithm is based in the dynamical algebra associated ...

We define a Wigner distribution function for a one-dimensional finite quantum system, in which the position and momentum operators have a finite (multiplicity-free) spectrum. The distribution function is thus defined on discrete phase-space, i.e. on a finite discrete square grid. These discrete Wigner functions possess a number of properties similar to the Wigner function for a continuous quant...

In nonintegrable Hamiltonian systems with mixed phase space and discrete symmetries, sequences of pitchfork bifurcations of periodic orbits pave the way from integrability to chaos. In extending the semiclassical trace formula for the spectral density, we develop a uniform approximation for the combined contribution of pitchfork bifurcation pairs. For a two-dimensional double-well potential and...

The Schrödinger equations for the Coulomb and the Harmonic oscillator potentials are solved in the cosmic-string conical space-time. The spherical harmonics with angular deficit are introduced. The algebraic construction of the harmonic oscillator eigenfunctions is performed through the introduction of non-local ladder operators. By exploiting the hidden symmetry of the two-dimensional harmonic...

The standard quantum limit constrains the precision of an oscillator position measurement. It arises from a balance between the imprecision and the quantum backaction of the measurement. However, a measurement of only a single quadrature of the oscillator can evade the backaction and be made with arbitrary precision. Here we demonstrate quantum backaction evading measurements of a collective qu...

In this second paper in a series of four, we continue with the program incorporating backreaction among homogeneous and between inhomogeneous degrees freedom quantum cosmological perturbation theory. The purpose present is to illustrate formalism space adiabatic theory for two simple mechanical models, prove that indeed leads additional correction terms effective Hamiltonians one would otherwis...

We prove the security of a quantum key distribution scheme based on transmission of squeezed quantum states of a harmonic oscillator. Our proof employs quantum error-correcting codes that encode a finitedimensional quantum system in the infinite-dimensional Hilbert space of an oscillator, and protect against errors that shift the canonical variables p and q. If the noise in the quantum channel ...

Abstract Quantum coherence, the ability of a quantum system to be in superposition orthogonal states, is distinct feature mechanics, thus marking deviation from classical physics. Coherence finds its applications sensing and metrology, thermodynamics computation. A particularly interesting possibility observe coherence arising counter-intuitive way thermal energy that without implementation int...