39
39

Sep 22, 2013
09/13

by
J. Eisert

texts

######
eye 39

######
favorite 0

######
comment 0

In this paper, the problem of finding optimal success probabilities of static linear optics quantum gates is linked to the theory of convex optimization. It is shown that by exploiting this link, upper bounds for the success probability of networks realizing single-mode gates can be derived, which hold in generality for linear optical networks followed by postselection, i.e., for networks of arbitrary size, any number of auxiliary modes, and arbitrary photon numbers. As a corollary, the...

Source: http://arxiv.org/abs/quant-ph/0409156v4

81
81

Jul 20, 2013
07/13

by
J. Eisert

texts

######
eye 81

######
favorite 0

######
comment 0

The density matrix renormalization group (DMRG) approach is arguably the most successful method to numerically find ground states of quantum spin chains. It amounts to iteratively locally optimizing matrix-product states, aiming at better and better approximating the true ground state. To date, both a proof of convergence to the globally best approximation and an assessment of its complexity are lacking. Here we establish a result on the computational complexity of an approximation with...

Source: http://arxiv.org/abs/quant-ph/0609051v3

161
161

Sep 19, 2013
09/13

by
J. Eisert

texts

######
eye 161

######
favorite 0

######
comment 0

This thesis covers several aspects of entanglement in the context of quantum information theory.

Source: http://arxiv.org/abs/quant-ph/0610253v1

37
37

Sep 21, 2013
09/13

by
J. Eisert

texts

######
eye 37

######
favorite 0

######
comment 0

In this paper it is shown that exact decoherence to minimal uncertainty Gaussian pointer states is generic for free quantum particles coupled to a heat bath. More specifically, the paper is concerned with damped free particles linearly coupled under product initial conditions to a heat bath at arbitrary temperature, with arbitrary coupling strength and spectral densities covering the Ohmic, subohmic, and supraohmic regime. Then it is true that there exists a time t_c such that for times...

Source: http://arxiv.org/abs/quant-ph/0311022v3

35
35

Sep 23, 2013
09/13

by
A. Mari; J. Eisert

texts

######
eye 35

######
favorite 0

######
comment 0

One of the main milestones in the study of opto- and electro-mechanical systems is to certify entanglement between a mechanical resonator and an optical or microwave mode of a cavity field. In this work, we show how a suitable time-periodic modulation can help to achieve large degrees of entanglement, building upon the framework introduced in [Phys. Rev. Lett. 103, 213603 (2009)]. It is demonstrated that with suitable driving, the maximum degree of entanglement can be significantly enhanced, in...

Source: http://arxiv.org/abs/1111.2415v1

42
42

Sep 19, 2013
09/13

by
J. Eisert; M. Wilkens

texts

######
eye 42

######
favorite 0

######
comment 0

We consider entanglement-assisted remote quantum state manipulation of bi-partite mixed states. Several aspects are addressed: we present a class of mixed states of rank two that can be transformed into another class of mixed states under entanglement-assisted local operations with classical communication, but for which such a transformation is impossible without assistance. Furthermore, we demonstrate enhancement of the efficiency of purification protocols with the help of...

Source: http://arxiv.org/abs/quant-ph/9912080v3

33
33

Sep 23, 2013
09/13

by
P. Hyllus; J. Eisert

texts

######
eye 33

######
favorite 0

######
comment 0

This paper is concerned with all tests for continuous-variable entanglement that arise from linear combinations of second moments or variances of canonical coordinates, as they are commonly used in experiments to detect entanglement. All such tests for bi-partite and multi-partite entanglement correspond to hyperplanes in the set of second moments. It is shown that all optimal tests, those that are most robust against imperfections with respect to some figure of merit for a given state, can be...

Source: http://arxiv.org/abs/quant-ph/0510077v3

92
92

Jul 20, 2013
07/13

by
D. Gross; J. Eisert

texts

######
eye 92

######
favorite 0

######
comment 0

We establish a framework which allows one to construct novel schemes for measurement-based quantum computation. The technique further develops tools from many-body physics - based on finitely correlated or projected entangled pair states - to go beyond the cluster-state based one-way computer. We identify resource states that are radically different from the cluster state, in that they exhibit non-vanishing correlation functions, can partly be prepared using gates with non-maximal entangling...

Source: http://arxiv.org/abs/quant-ph/0609149v3

66
66

Sep 22, 2013
09/13

by
J. Eisert; M. Wilkens

texts

######
eye 66

######
favorite 0

######
comment 0

In these lecture notes we investigate the implications of the identification of strategies with quantum operations in game theory beyond the results presented in [J. Eisert, M. Wilkens, and M. Lewenstein, Phys. Rev. Lett. 83, 3077 (1999)]. After introducing a general framework, we study quantum games with a classical analogue in order to flesh out the peculiarities of game theoretical settings in the quantum domain. Special emphasis is given to a detailed investigation of different sets of...

Source: http://arxiv.org/abs/quant-ph/0004076v1

33
33

Sep 23, 2013
09/13

by
D. Gross; J. Eisert

texts

######
eye 33

######
favorite 0

######
comment 0

We present a simple way to quantize the well-known Margulis expander map. The result is a quantum expander which acts on discrete Wigner functions in the same way the classical Margulis expander acts on probability distributions. The quantum version shares all essential properties of the classical counterpart, e.g., it has the same degree and spectrum. Unlike previous constructions of quantum expanders, our method does not rely on non-Abelian harmonic analysis. Analogues for continuous variable...

Source: http://arxiv.org/abs/0710.0651v2

35
35

Sep 21, 2013
09/13

by
K. Kieling; J. Eisert

texts

######
eye 35

######
favorite 0

######
comment 0

This article is a draft of a book chapter of the book entitled "Quantum Percolation and Breakdown", to appear 2008.

Source: http://arxiv.org/abs/0712.1836v1

6
6.0

Jun 27, 2018
06/18

by
C. Gogolin; J. Eisert

texts

######
eye 6

######
favorite 0

######
comment 0

We review selected advances in the theoretical understanding of complex quantum many-body systems with regard to emergent notions of quantum statistical mechanics. We cover topics such as equilibration and thermalisation in pure state statistical mechanics, the eigenstate thermalisation hypothesis, the equivalence of ensembles, non-equilibration dynamics following global and local quenches as well as ramps. We also address initial state independence, absence of thermalisation, and many-body...

Topics: Condensed Matter, Quantum Physics, Statistical Mechanics, Mathematics, Mathematical Physics,...

Source: http://arxiv.org/abs/1503.07538

32
32

Sep 21, 2013
09/13

by
J. Eisert; D. Gross

texts

######
eye 32

######
favorite 0

######
comment 0

When locally exciting a quantum lattice model, the excitation will propagate through the lattice. The effect is responsible for a wealth of non-equilibrium phenomena, and has been exploited to transmit quantum information through spin chains. It is a commonly expressed belief that for local Hamiltonians, any such propagation happens at a finite "speed of sound". Indeed, the Lieb-Robinson theorem states that in spin models, all effects caused by a perturbation are limited to a causal...

Source: http://arxiv.org/abs/0808.3581v3

30
30

Sep 21, 2013
09/13

by
A. Mari; J. Eisert

texts

######
eye 30

######
favorite 0

######
comment 0

We introduce the idea of actually cooling quantum systems by means of incoherent thermal light, hence giving rise to a counter-intuitive mechanism of "cooling by heating". In this effect, the mere incoherent occupation of a quantum mechanical mode serves as a trigger to enhance the coupling between other modes. This notion of effectively rendering states more coherent by driving with incoherent thermal quantum noise is applied here to the opto-mechanical setting, where this effect...

Source: http://arxiv.org/abs/1104.0260v1

30
30

Sep 23, 2013
09/13

by
J. Eisert; T. Prosen

texts

######
eye 30

######
favorite 0

######
comment 0

We discuss a notion of quantum critical exponents in open quantum many-body systems driven by quantum noise. We show that in translationally invariant quantum lattice models undergoing quasi-local Markovian dissipative processes, mixed states emerge as stationary points that show scaling laws for the divergence of correlation lengths giving rise to well-defined critical exponents. The main new technical tool developed here is a complete description of steady states of free bosonic or fermionic...

Source: http://arxiv.org/abs/1012.5013v1

43
43

Sep 20, 2013
09/13

by
J. Eisert; M. Cramer

texts

######
eye 43

######
favorite 0

######
comment 0

We introduce the single-copy entanglement as a quantity to assess quantum correlations in the ground state in quantum many-body systems. We show for a large class of models that already on the level of single specimens of spin chains, criticality is accompanied with the possibility of distilling a maximally entangled state of arbitrary dimension from a sufficiently large block deterministically, with local operations and classical communication. These analytical results -- which refine previous...

Source: http://arxiv.org/abs/quant-ph/0506250v3

38
38

Sep 18, 2013
09/13

by
M. Cramer; J. Eisert

texts

######
eye 38

######
favorite 0

######
comment 0

We investigate the relationship between the gap between the energy of the ground state and the first excited state and the decay of correlation functions in harmonic lattice systems. We prove that in gapped systems, the exponential decay of correlations follows for both the ground state and thermal states. Considering the converse direction, we show that an energy gap can follow from algebraic decay and always does for exponential decay. The underlying lattices are described as general graphs...

Source: http://arxiv.org/abs/quant-ph/0509167v3

33
33

Sep 23, 2013
09/13

by
D. Gross; J. Eisert

texts

######
eye 33

######
favorite 0

######
comment 0

We introduce the notion of quantum computational webs: These are quantum states universal for measurement-based computation which can be built up from a collection of simple primitives. The primitive elements - reminiscent of building blocks in a construction kit - are (i) states on a one-dimensional chain of systems ("computational quantum wires") with the power to process one logical qubit and (ii) suitable couplings which connect the wires to a computationally universal...

Source: http://arxiv.org/abs/0810.2542v2

49
49

Sep 18, 2013
09/13

by
J. Eisert; D. Gross

texts

######
eye 49

######
favorite 0

######
comment 0

We review the theory of multi-particle entanglement. In this book chapter we aim at briefly ``setting the coordinates'' and guiding through the extensive literature in this field. Our coordinate system chosen for this chapter has the axes labeled pure and mixed states on the one hand, entanglement in single specimens and the asymptotic setting on the other hand. We very briefly mention ways to detect multi-particle entanglement, and introduce the concepts of stabilizer and graph states.

Source: http://arxiv.org/abs/quant-ph/0505149v2

63
63

Sep 18, 2013
09/13

by
H. M. Wiseman; J. Eisert

texts

######
eye 63

######
favorite 0

######
comment 0

Invited contribution to "Quantum Aspects of Life", D. Abbott Ed. (World Scientific, Singapore, 2007).

Source: http://arxiv.org/abs/0705.1232v2

230
230

Sep 18, 2013
09/13

by
J. Eisert; M. M. Wolf

texts

######
eye 230

######
favorite 1

######
comment 0

This article gives an elementary introduction to quantum computing. It is a draft for a book chapter of the "Handbook of Nature-Inspired and Innovative Computing", Eds. A. Zomaya, G.J. Milburn, J. Dongarra, D. Bader, R. Brent, M. Eshaghian-Wilner, F. Seredynski (Springer, Berlin Heidelberg New York, 2006).

Source: http://arxiv.org/abs/quant-ph/0401019v3

33
33

Sep 23, 2013
09/13

by
J. Eisert; M. B. Plenio

texts

######
eye 33

######
favorite 0

######
comment 0

We present a general necessary and sufficient criterion for the possibility of a state transformation from one mixed Gaussian state to another of a bi-partite continuous-variable system with two modes. The class of operations that will be considered is the set of local Gaussian completely positive trace-preserving maps.

Source: http://arxiv.org/abs/quant-ph/0109126v2

32
32

Sep 22, 2013
09/13

by
J. Eisert; M. B. Plenio

texts

######
eye 32

######
favorite 0

######
comment 0

We investigate the entanglement properties of the joint state of a distinguished quantum system and its environment in the quantum Brownian motion model. This model is a frequent starting point for investigations of environment-induced superselection. Using recent methods from quantum information theory, we show that there exists a large class of initial states for which no entanglement will be created at all times between the system of salient interest and the environment. If the distinguished...

Source: http://arxiv.org/abs/quant-ph/0111016v3

45
45

Sep 23, 2013
09/13

by
J. Eisert; M. B. Plenio

texts

######
eye 45

######
favorite 0

######
comment 0

We outline the basic questions that are being studied in the theory of entanglement. Following a brief review of some of the main achievements of entanglement theory for finite-dimensional quantum systems such as qubits, we will consider entanglement in infinite-dimensional systems. Asking for a theory of entanglement in such systems under experimentally feasible operations leads to the development of the theory of entanglement of Gaussian states. Results of this theory are presented and the...

Source: http://arxiv.org/abs/quant-ph/0312071v2

39
39

Sep 22, 2013
09/13

by
J. Eisert; M. B. Plenio

texts

######
eye 39

######
favorite 0

######
comment 0

We compare the entanglement of formation with a measure defined as the modulus of the negative eigenvalue of the partial transpose. In particular, we investigate whether both measures give the same ordering of density operators with respect to the amount of entanglement.

Source: http://arxiv.org/abs/quant-ph/9807034v2

47
47

Sep 18, 2013
09/13

by
J. Eisert; M. M. Wolf

texts

######
eye 47

######
favorite 0

######
comment 0

This article provides an elementary introduction to Gaussian channels and their capacities. We review results on the classical, quantum, and entanglement assisted capacities and discuss related entropic quantities as well as additivity issues. Some of the known results are extended. In particular, it is shown that the quantum conditional entropy is maximized by Gaussian states and that some implications for additivity problems can be extended to the Gaussian setting.

Source: http://arxiv.org/abs/quant-ph/0505151v1

33
33

Sep 24, 2013
09/13

by
M. M. Wolf; J. Eisert

texts

######
eye 33

######
favorite 0

######
comment 0

We consider the additivity of the minimal output entropy and the classical information capacity of a class of quantum channels. For this class of channels the norm of the output is maximized for the output being a normalized projection. We prove the additivity of the minimal output Renyi entropies with entropic parameters contained in [0, 2], generalizing an argument by Alicki and Fannes, and present a number of examples in detail. In order to relate these results to the classical information...

Source: http://arxiv.org/abs/quant-ph/0412133v3

52
52

Sep 17, 2013
09/13

by
J. Eisert; H. -J. Briegel

texts

######
eye 52

######
favorite 0

######
comment 0

We present a measure of quantum entanglement which is capable of quantifying the degree of entanglement of a multi-partite quantum system. This measure, which is based on a generalization of the Schmidt rank of a pure state, is defined on the full state space and is shown to be an entanglement monotone, that is, it cannot increase under local quantum operations with classical communication and under mixing. For a large class of mixed states this measure of entanglement can be calculated...

Source: http://arxiv.org/abs/quant-ph/0007081v3

0
0.0

Jun 30, 2018
06/18

by
M. Kliesch; D. Gross; J. Eisert

texts

######
eye 0

######
favorite 0

######
comment 0

Tensor network states constitute an important variational set of quantum states for numerical studies of strongly correlated systems in condensed-matter physics, as well as in mathematical physics. This is specifically true for finitely correlated states or matrix-product operators, designed to capture mixed states of one-dimensional quantum systems. It is a well-known open problem to find an efficient algorithm that decides whether a given matrix-product operator actually represents a physical...

Topics: Quantum Physics, Mathematics, Strongly Correlated Electrons, Mathematical Physics, Condensed Matter

Source: http://arxiv.org/abs/1404.4466

28
28

Sep 18, 2013
09/13

by
M. Cramer; A. Serafini; J. Eisert

texts

######
eye 28

######
favorite 0

######
comment 0

The Lieb-Robinson theorem states that locality is approximately preserved in the dynamics of quantum lattice systems. Whenever one has finite-dimensional constituents, observables evolving in time under a local Hamiltonian will essentially grow linearly in their support, up to exponentially suppressed corrections. In this work, we formulate Lieb-Robinson bounds for general harmonic systems on general lattices, for which the constituents are infinite-dimensional, as systems representing discrete...

Source: http://arxiv.org/abs/0803.0890v2

5
5.0

Jun 27, 2018
06/18

by
R. Gallego; J. Eisert; H. Wilming

texts

######
eye 5

######
favorite 0

######
comment 0

In recent years we have witnessed a concentrated effort to make sense of thermodynamics for small-scale systems. One of the main difficulties is to capture a suitable notion of work that models realistically the purpose of quantum machines, in an analogous way to the role played, for macroscopic machines, by the energy stored in the idealisation of a lifted weight. Despite of several attempts to resolve this issue by putting forward specific models, these are far from capturing realistically...

Topics: Condensed Matter, Quantum Physics, Statistical Mechanics, Mathematics, Mathematical Physics

Source: http://arxiv.org/abs/1504.05056

30
30

Sep 19, 2013
09/13

by
K. Kieling; D. Gross; J. Eisert

texts

######
eye 30

######
favorite 0

######
comment 0

Several physical architectures allow for measurement-based quantum computing using sequential preparation of cluster states by means of probabilistic quantum gates. In such an approach, the order in which partial resources are combined to form the final cluster state turns out to be crucially important. We determine the influence of this classical decision process on the expected size of the final cluster. Extending earlier work, we consider different quantum gates operating at various...

Source: http://arxiv.org/abs/quant-ph/0703045v2

64
64

Sep 17, 2013
09/13

by
K. Audenaert; M. B. Plenio; J. Eisert

texts

######
eye 64

######
favorite 0

######
comment 0

We study the entanglement cost under quantum operations preserving the positivity of the partial transpose (PPT-operations). We demonstrate that this cost is directly related to the logarithmic negativity, thereby providing the operational interpretation for this easily computable entanglement measure. As examples we discuss general Werner states and arbitrary bi-partite Gaussian states. Equipped with this result we then prove that for the anti-symmetric Werner state PPT-cost and...

Source: http://arxiv.org/abs/quant-ph/0207146v1

30
30

Sep 18, 2013
09/13

by
D. Gross; K. Kieling; J. Eisert

texts

######
eye 30

######
favorite 0

######
comment 0

We establish bounds to the necessary resource consumption when building up cluster states for one-way computing using probabilistic gates. Emphasis is put on state preparation with linear optical gates, as the probabilistic character is unavoidable here. We identify rigorous general bounds to the necessary consumption of initially available maximally entangled pairs when building up one-dimensional cluster states with individually acting linear optical quantum gates, entangled pairs and vacuum...

Source: http://arxiv.org/abs/quant-ph/0605014v2

99
99

Sep 23, 2013
09/13

by
J. Eisert; M. P. Mueller; C. Gogolin

texts

######
eye 99

######
favorite 0

######
comment 0

In this work, we show that very natural, apparently simple problems in quantum measurement theory can be undecidable even if their classical analogues are decidable. Undecidability hence appears as a genuine quantum property here. Formally, an undecidable problem is a decision problem for which one cannot construct a single algorithm that will always provide a correct answer in finite time. The problem we consider is to determine whether sequentially used identical Stern-Gerlach-type...

Source: http://arxiv.org/abs/1111.3965v3

36
36

Sep 18, 2013
09/13

by
J. Eisert; K. Audenaert; M. B. Plenio

texts

######
eye 36

######
favorite 0

######
comment 0

We investigate the properties of three entanglement measures that quantify the statistical distinguishability of a given state with the closest disentangled state that has the same reductions as the primary state. In particular, we concentrate on the relative entropy of entanglement with reversed entries. We show that this quantity is an entanglement monotone which is strongly additive, thereby demonstrating that monotonicity under local quantum operations and strong additivity are compatible...

Source: http://arxiv.org/abs/quant-ph/0212007v1

30
30

Sep 20, 2013
09/13

by
K. Kieling; D. Gross; J. Eisert

texts

######
eye 30

######
favorite 0

######
comment 0

We address the question of how many maximally entangled photon pairs are needed in order to build up cluster states for quantum computing using the toolbox of linear optics. As the needed gates in dual-rail encoding are necessarily probabilistic with known optimal success probability, this question amounts to finding the optimal strategy for building up cluster states, from the perspective of classical control. We develop a notion of classical strategies, and present rigorous statements on the...

Source: http://arxiv.org/abs/quant-ph/0601190v2

0
0.0

Jun 30, 2018
06/18

by
R. Hübener; Y. Sekino; J. Eisert

texts

######
eye 0

######
favorite 0

######
comment 0

Matrix models play an important role in studies of quantum gravity, being candidates for a formulation of M-theory, but are notoriously difficult to solve. In this work, we present a fresh approach by introducing a novel exact model provably equivalent with low-dimensional bosonic matrix models. In this equivalent model significant local structure becomes apparent and it can serve as a simple toy model for analytical and precise numerical study. We derive a substantial part of the low energy...

Topics: Quantum Physics, High Energy Physics - Theory, Nonlinear Sciences, Chaotic Dynamics

Source: http://arxiv.org/abs/1403.1392

37
37

Sep 22, 2013
09/13

by
M. Hein; J. Eisert; H. J. Briegel

texts

######
eye 37

######
favorite 0

######
comment 0

Graph states are multi-particle entangled states that correspond to mathematical graphs, where the vertices of the graph take the role of quantum spin systems and edges represent Ising interactions. They are many-body spin states of distributed quantum systems that play a significant role in quantum error correction, multi-party quantum communication, and quantum computation within the framework of the one-way quantum computer. We characterize and quantify the genuine multi-particle...

Source: http://arxiv.org/abs/quant-ph/0307130v7

27
27

Sep 21, 2013
09/13

by
C. Pineda; T. Barthel; J. Eisert

texts

######
eye 27

######
favorite 0

######
comment 0

We introduce a scheme for efficiently describing pure states of strongly correlated fermions in higher dimensions using unitary circuits featuring a causal cone. A local way of computing local expectation values is presented. We formulate a dynamical reordering scheme, corresponding to time-adaptive Jordan-Wigner transformation, that avoids nonlocal string operators. Primitives of such a reordering scheme are highlighted. Fermionic unitary circuits can be contracted with the same complexity as...

Source: http://arxiv.org/abs/0905.0669v3

81
81

Sep 21, 2013
09/13

by
J. Eisert; M. Cramer; M. B. Plenio

texts

######
eye 81

######
favorite 0

######
comment 0

Physical interactions in quantum many-body systems are typically local: Individual constituents interact mainly with their few nearest neighbors. This locality of interactions is inherited by a decay of correlation functions, but also reflected by scaling laws of a quite profound quantity: The entanglement entropy of ground states. This entropy of the reduced state of a subregion often merely grows like the boundary area of the subregion, and not like its volume, in sharp contrast with an...

Source: http://arxiv.org/abs/0808.3773v4

43
43

Sep 20, 2013
09/13

by
J. Eisert; S. Scheel; M. B. Plenio

texts

######
eye 43

######
favorite 0

######
comment 0

We show that no distillation protocol for Gaussian quantum states exists that relies on (i) arbitrary local unitary operations that preserve the Gaussian character of the state and (ii) homodyne detection together with classical communication and postprocessing by means of local Gaussian unitary operations on two symmetric identically prepared copies. This is in contrast to the finite-dimensional case, where entanglement can be distilled in an iterative protocol using two copies at a time. The...

Source: http://arxiv.org/abs/quant-ph/0204052v4

40
40

Sep 19, 2013
09/13

by
K. Kieling; J. L. O'Brien; J. Eisert

texts

######
eye 40

######
favorite 0

######
comment 0

As primitives for entanglement generation, controlled phase gates take a central role in quantum computing. Especially in ideas realizing instances of quantum computation in linear optical gate arrays a closer look can be rewarding. In such architectures, all effective non-linearities are induced by measurements: Hence the probability of success is a crucial parameter of such quantum gates. In this note, we discuss this question for controlled phase gates that implement an arbitrary phase with...

Source: http://arxiv.org/abs/0909.2057v4

29
29

Sep 20, 2013
09/13

by
R. Hübener; A. Mari; J. Eisert

texts

######
eye 29

######
favorite 0

######
comment 0

Matrix-product states and their continuous analogues are variational classes of states that capture quantum many-body systems or quantum fields with low entanglement; they are at the basis of the density-matrix renormalization group method and continuous variants thereof. In this work we show that, generically, N-point functions of arbitrary operators in discrete and continuous translationally invariant matrix product states are completely characterized by the corresponding two- and three-point...

Source: http://arxiv.org/abs/1207.6537v2

74
74

Sep 18, 2013
09/13

by
M. Cramer; J. Eisert; M. B. Plenio

texts

######
eye 74

######
favorite 0

######
comment 0

The entanglement entropy of a distinguished region of a quantum many-body system reflects the entanglement present in its pure ground state. In this work, we establish scaling laws for this entanglement for critical quasi-free fermionic and bosonic lattice systems, without resorting to numerical means. We consider the geometrical setting of D-dimensional half-spaces which allows us to exploit a connection to the one-dimensional case. Intriguingly, we find a difference in the scaling properties...

Source: http://arxiv.org/abs/quant-ph/0611264v4

75
75

Sep 23, 2013
09/13

by
D. Gross; S. Flammia; J. Eisert

texts

######
eye 75

######
favorite 0

######
comment 0

It is often argued that entanglement is at the root of the speedup for quantum compared to classical computation, and that one needs a sufficient amount of entanglement for this speedup to be manifest. In measurement-based quantum computing (MBQC), the need for a highly entangled initial state is particularly obvious. Defying this intuition, we show that quantum states can be too entangled to be useful for the purpose of computation. We prove that this phenomenon occurs for a dramatic majority...

Source: http://arxiv.org/abs/0810.4331v3

30
30

Sep 21, 2013
09/13

by
M. B. Plenio; J. Hartley; J. Eisert

texts

######
eye 30

######
favorite 0

######
comment 0

We study the entanglement dynamics of a system consisting of a large number of coupled harmonic oscillators in various configurations and for different types of nearest neighbour interactions. For a one-dimensional chain we provide compact analytical solutions and approximations to the dynamical evolution of the entanglement between spatially separated oscillators. Key properties such as the speed of entanglement propagation, the maximum amount of transferred entanglement and the efficiency for...

Source: http://arxiv.org/abs/quant-ph/0402004v2

32
32

Sep 18, 2013
09/13

by
K. Kieling; T. Rudolph; J. Eisert

texts

######
eye 32

######
favorite 0

######
comment 0

We apply a notion of static renormalization to the preparation of entangled states for quantum computing, exploiting ideas from percolation theory. Such a strategy yields a novel way to cope with the randomness of non-deterministic quantum gates. This is most relevant in the context of optical architectures, where probabilistic gates are common, and cold atoms in optical lattices, where hole defects occur. We demonstrate how to efficiently construct cluster states without the need for...

Source: http://arxiv.org/abs/quant-ph/0611140v3

0
0.0

Jun 29, 2018
06/18

by
J. Eisert; V. Eisler; Z. Zimborás

texts

######
eye 0

######
favorite 0

######
comment 0

The entanglement negativity is a versatile measure of entanglement that has numerous applications in quantum information and in condensed matter theory. It can not only efficiently be computed in the Hilbert space dimension, but for non-interacting bosonic systems, one can compute the negativity efficiently in the number of modes. However, such an efficient computation does not carry over to the fermionic realm, the ultimate reason for this being that the partial transpose of a fermionic...

Topics: Quantum Physics, Condensed Matter, Other Condensed Matter

Source: http://arxiv.org/abs/1611.08007

34
34

Sep 21, 2013
09/13

by
M. Ohliger; V. Nesme; J. Eisert

texts

######
eye 34

######
favorite 0

######
comment 0

We present a novel method to perform quantum state tomography for many-particle systems which are particularly suitable for estimating states in lattice systems such as of ultra-cold atoms in optical lattices. We show that the need for measuring a tomographically complete set of observables can be overcome by letting the state evolve under some suitably chosen random circuits followed by the measurement of a single observable. We generalize known results about the approximation of unitary...

Source: http://arxiv.org/abs/1204.5735v2