We provide a physical prescription based on interferometry for introducing the total phase of mixed state undergoing unitary evolution, which has been an elusive concept in past. define parallel transport condition that provides connection form obtaining geometric states. The expression reduces to well known formulas pure case when system undergoes noncyclic and quantum evolution.

We develop a non-adiabatic generalization of holonomic quantum computation in which high-speed universal gates can be realized by using non-Abelian geometric phases. show how set one- and two-qubit implemented utilizing optical transitions generic three-level $\Lambda$ configuration. Our scheme opens up for on qubits characterized short coherence times.

Quantum computation that combines the coherence stabilization virtues of decoherence-free subspaces and fault tolerance geometric holonomic control is great practical importance. Some schemes adiabatic quantum in have been proposed past few years. However, nonadiabatic subspaces, which avoids a long run-time requirement but with all robust advantages, remains an open problem. Here, we demonstrate how to realize subspaces. By using only three neighboring physical qubits undergoing collective...

A kinematic approach to the geometric phase for mixed quantal states in nonunitary evolution is proposed. This manifestly gauge invariant and can be experimentally tested interferometry. It leads well-known results when unitary.

The robustness to different sources of error the scheme for non-adiabatic holonomic gates proposed in [New J. Phys. {\bf 14}, 103035 (2012)] is investigated. Open system effects as well errors driving fields are considered. It found that can be made resilient by using sufficiently short pulses. principal limit how pulses given breakdown quasi-monochromatic approximation. A comparison with resilience adiabatic carried out.

Nonadiabatic geometric quantum computation provides a means to perform fast and robust gates. It has been implemented in various physical systems, such as trapped ions, nuclear magnetic resonance superconducting circuits. Another system being adequate for implementation of nonadiabatic may be Rydberg atoms, since their internal states have very long coherence time the Rydberg-mediated interaction facilitates two-qubit gate. Here, we propose scheme based on which combines robustness gates...

Abstract A practical quantum computer must be capable of performing high fidelity gates on a set bits (qubits). In the presence noise, realization such poses daunting challenges. Geometric phases, which possess intrinsic noise-tolerant features, hold promise for robust computation. particular, holonomies, i.e., non-Abelian geometric naturally lead to universal computation due their non-commutativity. Although based adiabatic holonomies have already been proposed, slow evolution eventually...

Nonadiabatic holonomic quantum computation provides the means to perform fast and robust gates by utilizing resilience of non-Abelian geometric phases fluctuations path in state space. While original scheme [E. Sj\"oqvist et al., New J. Phys. 14, 103035 (2012)] needs two loops Grassmann manifold (i.e., space computational subspaces full space) generate an arbitrary one-qubit gate, we propose single-loop that constitute efficient universal set when combined with entangling two-qubit gate. Our...

Magnetoelasticity plays a crucial role in numerous magnetic phenomena, including magnetocalorics, magnon excitation via acoustic waves, and ultrafast demagnetization, or the Einstein–de Haas effect. Despite long-standing discussion on anisotropy-mediated magnetoelastic interactions of relativistic origin, exchange-mediated parameters within an atomistic framework have only recently begun to be investigated. As result, many their behaviors values for real materials remain poorly understood....

Large-scale quantum computers are hard to construct because systems easily lose their coherence through interaction with the environment. Researchers have tried avoid this problem by using geometric phase shifts in design of gates perform information processing. Experiments and simulations shown that these may be tolerant certain types faults, therefore useful for robust computation.

The rise of quantum information science has opened up a new venue for applications the geometric phase (GP), as well triggered insights into its physical, mathematical, and conceptual nature. Here, we review this development by focusing on three main themes: use GPs to perform robust computation, GP concepts mixed states, discovery type topological phases entangled systems. We delineate theoretical describe recent experiments related in context information. © 2015 Wiley Periodicals, Inc.

Quantum information processing requires a high degree of isolation from the detrimental effects environment as well an extremely precise level control on way quantum dynamics unfolds in information-processing system. In this paper, we show how these two goals can be ideally achieved by hybridizing concepts noiseless subsystems and holonomic computation. An all-geometric universal computation scheme based non-adiabatic non-Abelian holonomies embedded four-qubit subsystem for general...

Nonadiabatic holonomic quantum computation in decoherence-free subspaces has attracted increasing attention recently, as it allows for high-speed implementation and combines both the robustness of gates coherence stabilization subspaces. Since first protocol nonadiabatic subspaces, a number schemes its physical have been put forward. However, all previous require two noncommuting to realize an arbitrary one-qubit gate, which doubles exposure time error sources well resource expenditure. In...

The entanglement dependence of the noncyclic geometric phase is analyzed. A pair noninteracting spin-$\frac{1}{2}$ particles prepared in an arbitrarily entangled state and precessing external time-independent uniform magnetic field considered. It shown that reduces to a sum one-particle phases for product states takes on two values corresponding factors $\ifmmode\pm\else\textpm\fi{}1$ maximally states. If only one affected by it demonstrated influence may be interpreted as effective...

An atomic analogue of Landau quantization based on the Aharonov-Casher (AC) interaction is developed. The effect provides a first step towards an quantum Hall system using electric fields, which may be realized in Bose-Einstein condensate.

Geometric manipulation of a quantum system offers method for fast, universal and robust information processing. Here, we propose scheme all-geometric computation using non-adiabatic holonomies. We three different realizations the based on an unconventional use dot single-molecule magnet devices, which offer promising scalability efficiency.

Nonadiabatic holonomic quantum computation has robust feature in suppressing control errors because of its feature. However, this kind is challenged since the usual way realizing nonadiabatic gates introduces due to systematic parameters. To resolve problem, we here propose a composite scheme realize gates. Our can suppress while preserving robustness. It particularly useful when evolution period shorter than coherence time. We further show that our be protected by decoherence-free...

Quantum magnonics is an emerging research field, with great potential for applications in magnon based hybrid systems and quantum information processing. correlation, such as entanglement, a central resource many protocols that naturally comes about any study toward technologies. This applies also to magnonics. Here, we investigate antiferromagnets which sublattices ferromagnetic interactions can have two different modes, show how this may lead experimentally detectable bipartite continuous...

Abstract Despite decades of research, the role lattice and its coupling to magnetisation during ultrafast demagnetisation processes is still not fully understood. Here we report on studies both explicit implicit effects laser induced bcc Fe fcc Co. We do this using atomistic spin- dynamics simulations following a heat-conserving three-temperature model. show that type Langevin-based simulation able reproduce observed trends magnetization Co Fe. The parameters used in our models are all...

We generalize the notion of relative phase to completely positive (CP) maps with known unitary representation, based on interferometry. Parallel transport conditions that define geometric for such are introduced. The interference effect is embodied in a set patterns defined by flipping environment state one two paths. show qubit this structure gives rise interesting additional information about geometry evolution CP map.