Abstract Holonomic quantum computation (HQC) may not show its full potential in speedup due to the prerequisite of a long coherent runtime imposed by adiabatic condition. Here we that conventional HQC can be dramatically accelerated using external control fields, which effectiveness is exclusively determined integral fields time domain. This scheme realized with net zero energy cost and it fault-tolerant against fluctuation noise, significantly relaxing experimental constraints. We...

We prove that there exists a family of quantum systems can be cooled to their ground states by one-shot projective measurement on the ancillas coupled these systems. Consequently, this proof gives rise conditions for achieving ground-state cooling (OSMGSC). also propose general procedure finding unitary propagators and corresponding Hamiltonians realize such means inverse engineering techniques.

We find dynamical invariants for open quantum systems described by the non-Markovian quantum-state-diffusion (QSD) equation. In stark contrast to closed where invariant can be identical system density operator, these no longer share equation of motion operator. Moreover, obtained with a biorthonormal basis used render an exact solution QSD and corresponding dynamics without using master equations or numerical simulations. Significantly we show that apply reverse engineering Hamiltonian is...

We propose spintronic systems which spin dynamics is determined by the frequent normal electron collisions. Spin oscillation induced electrical field predicted. The hydrodynamic equations for spin-polarized liquid have been obtained and analyzed. found that in case of a conducting magnetic-inhomogeneous ring, both polarization drift current may oscillate simultaneously with large decay time (``spin pendulum''). demonstrate also density be revealed via voltage between ends open circuit an...

We study optimization of fidelity for ultrafast transformation a spin chain via external control local exchange coupling. show that infidelity such process can be dramatically decreased by choosing proper profile in nonadiabatic time domain, predict main features this analytically, corroborate them numerically with gradient search algorithm, and discuss the corresponding quantum speed limit. For transformations, qualitative obtained optimal are system independent. Moreover, restrictions on...

Recent experiments show the existence of collective decoherence in quantum systems. We study possibility computation a decoherence-free subspace which is robust against such kinds processes. This passive protection protocol can be especially advantageous for continuous as annealers. As an example we propose to use decoherence-protected adiabatic Grover search problem.

We propose and analyze, focusing on non-adiabatic effects, a technique of manipulating quantum spin systems based local 'cutting' 'stitching' the Heisenberg exchange coupling between spins. This first operation is cutting bond separating single from linear chain, or two neighboring bonds for ring-shaped array show that disconnected can be in ground state with high-fidelity even after process. Next, we consider inverse stitching these to increase system size. optimal control algorithm found...

We propose a scheme for engineering compressed spatial states in two-dimensional parabolic potential with spin-orbit coupling by selective spin measurements. This sequence of measurements results coordinate-dependent density matrix probability maxima achieved at set lines or lattice. The resultant depends on the and parameters allows one to obtain broad class localized pure demand. proposed can be realized spin-orbit-coupled Bose-Einstein condensates.

Transport phenomena are examined in electron systems on liquid helium surfaces strong nonquantizing nonuniform magnetic fields. For applied electric fields with frequencies low enough that an equilibrium distribution of the spins along conducting surface can develop during wave period, electrical resistance is determined by different current carrier scattering processes than uniform case. Spin nonuniformity makes electron-electron collisions efficient respect to momentum loss, so...

Holonomic quantum computation (HQC) may not show its full potential in speedup due to the prerequisite of a long coherent runtime imposed by adiabatic condition. Here we that conventional HQC can be dramatically accelerated using external control fields, which effectiveness is exclusively determined integral fields time domain. Remarkably this scheme realized with net zero energy cost and it fault-tolerant against fluctuation noise, significantly relaxing experimental constraints. We...

A study is made of the natural spin-electric and thermoelectric oscillations in an electron ring forced spin density temperature driven with help external electrodes. Effects that may be used to investigate characteristics system, particular, spin-flip processes, by means electrical measurements are proposed.

We provide an alternative approach to relativistic dynamics based on the Feshbach projection technique. Instead of directly studying Dirac equation, we derive a two-component equation for upper spinor. This allows one investigate underlying physics in different perspective. For particles with small mass such as neutrino, leading-order has Hermitian effective Hamiltonian, implying there is no leakage between and lower spinors. In weak regime, leading order corresponds non-Hermitian correction...

We examine 2D electron transport through a long narrow channel driven by an external electric field in presence of diffusive boundary scattering. At zero temperature, we derive analytical solution the transition from ballistic to if increase bulk disorder strength. This crossover yields characteristic current density profiles. Furthermore, illustrate hydrodynamic transport. corresponds Gurzhi effect resistivity. also study influence finite temperature on densities and average this system. In...

We consider transformation from a closed to an open spin chain and vice versa produced by changing single link strength in pair of neighboring spins.We show that the non-adiabatic time domain fidelity such process can be increased proper choosing control function for spin-spin exchange coupling.We obtain this antiferromagnetic quantum Ising present heuristic reasons restricting possible timedependences Hamiltonians applied high-fidelity control.

Usually, the evidence of viscous hydrodynamic transport frequently colliding conduction electrons is considered to be “Gurzhi effect,” which requires scattering on channel walls with momentum loss. However, we demonstrate that expansion Sharvin’s potential drop directly related frequent electron-electron collisions can detected even in channels ideally smooth a two-dimensional degenerate electron gas (2DEG). In theory, this effect could experimental predicted earlier difference between...

Abstract Precise control of quantum systems with a moderate number degrees freedom,
 being interest for application in technologies, becomes experimentally feasible. 
 Various types scenarios and protocols are widely discussed scientific literature. We propose, analyze, optimize protocol which allows fast simulation properties unknown states relying on minimum relevant information. Our protocol, having common features identification shortcuts to adiabaticity,
 permits...

Lagrangian of electronic liquid in magneto-inhomogeneous micro-conductor has been constructed. A corresponding Euler-Lagrange equation solved. It was shown that the described system eigenmodes spin polarization and total electric current oscillations. The suggested approach permits to study dynamics an open-circuit which contains capacitance and/or inductivity.

The real part of the conductance a 1D conducting ring with magnetic properties that vary along conductor is examined. possibility exciting new type spin polarization oscillations in an external emf analyzed.

We propose and analyze a nonunitary variant of the continuous time Grover search algorithm based on frequent Zeno-type measurements. show that scales similarly to pure quantum version by deriving tight analytical lower bounds its efficiency for arbitrary database sizes measurement parameters. also study behavior subject noise, find under certain oracle operational errors our measurement-based outperforms standard algorithm, showing robustness against these noises. Our analysis is...

We present a high-rate projective measurement-based approach for controlling nonunitary evolution of quantum chain interacting spins. In this approach, we demonstrate that local measurement single external spin coupled to the can produce polaron, which remains stable after end measurement. This stability results from fact Hilbert space contains subspace nondecaying states, during evolution. These states determine resulting final state and long-term shape polaron. addition formation polarons,...