Exact convergence rates for arbitrary statistical moments of random quantum circuits (2009)
Brown, Winton G., Viola, Lorenza
We consider a general class of random quantum circuits where at each step a gate from a universal set is applied to a random pair of qubits, and provide a complete solution to the problem of...
Anomalous non-ergodic scaling in adiabatic multicritical quantum quenches (2009)
Deng, Shusa, Ortiz, Gerardo, Viola, Lorenza
We investigate non-equilibrium dynamical scaling in adiabatic quench processes across quantum multicritical points. Our analysis shows that the resulting power-law scaling depends sensitively on the...
Arbitrarily Accurate Dynamical Control in Open Quantum Systems (2009)
Khodjasteh, Kaveh, Lidar, Daniel A., Viola, Lorenza
We show that open-loop dynamical control techniques may be used to synthesize unitary transformations in open quantum systems in such a way that decoherence is perturbatively compensated for to a...
Zhang, Wenxian, Cappellaro, Paola, Antler, Natania, Pepper, Brian, Cory, David G., Dobrovitski, Viatcheslav V., ...
The 19F spins in a crystal of fluorapatite have often been used to experimentally approximate a one-dimensional spin system. Under suitable multi-pulse control, the nuclear spin dynamics may be...
Dynamical Quantum Error Correction of Unitary Operations with Bounded Controls (2009)
Khodjasteh, Kaveh, Viola, Lorenza
Dynamically corrected gates were recently introduced [Khodjasteh and Viola, Phys. Rev. Lett. 102, 080501 (2009)] as a tool to achieve decoherence-protected quantum gates based on open-loop...
Dynamically Error-Corrected Gates for Universal Quantum Computation (2008)
Khodjasteh, Kaveh, Viola, Lorenza
Scalable quantum computation in realistic devices requires that precise control can be implemented efficiently in the presence of decoherence and operational errors. We propose a general constructive...
Dynamical non-ergodic scaling in continuous finite-order quantum phase transitions (2008)
Deng, Shusa, Ortiz, Gerardo, Viola, Lorenza
We investigate the emergence of universal dynamical scaling in quantum critical spin systems adiabatically driven out of equilibrium, with emphasis on quench dynamics which involves non-isolated...
Analysis and synthesis of attractive quantum Markovian dynamics (2008)
Ticozzi, Francesco, Viola, Lorenza
We propose a general framework for investigating a large class of stabilization problems in Markovian quantum systems. Building on the notions of invariant and attractive quantum subsystem, we...
Parameters of Pseudo-Random Quantum Circuits (2008)
Weinstein, Yaakov S., Brown, Winton G., Viola, Lorenza
Pseudorandom circuits generate quantum states and unitary operators which are approximately distributed according to the unitarily invariant Haar measure. We explore how several design parameters...
Advantages of Randomization in Coherent Quantum Dynamical Control (2008)
Santos, Lea F., Viola, Lorenza
Control scenarios have been identified where the use of randomized design may substantially improve the performance of dynamical decoupling methods [L. F. Santos and L. Viola, Phys. Rev. Lett. {\bf...
Suppression of exciton dephasing in quantum dots through ultrafast multipulse control (2008)
Hodgson, Thomas E., Viola, Lorenza, D'Amico, Irene
We investigate the usefulness and viability of the scheme developed by Viola and Lloyd [Phys. Rev. A 58, 2733 (1998)] to control dephasing in the context of exciton-based quantum computation with...
Generalized entanglement in static and dynamic quantum phase transitions (2008)
Deng, Shusa, Ortiz, Gerardo, Viola, Lorenza
We investigate a class of one-dimensional, exactly solvable anisotropic XY spin-1/2 models in an alternating transverse magnetic field from an entanglement perspective. We find that a physically...
Quantum pseudo-randomness from cluster-state quantum computation (2008)
Brown, Winton G., Weinstein, Yaakov S., Viola, Lorenza
We show how to efficiently generate pseudo-random states suitable for quantum information processing via cluster-state quantum computation. By reformulating pseudo-random algorithms in the...
Characterizing the Structure of Preserved Information in Quantum Processes (2008)
Blume-Kohout, Robin, Ng, Hui Khoon, Poulin, David, Viola, Lorenza
We introduce a general operational characterization of information-preserving structures—encompassing noiseless subsystems, decoherence-free subspaces, pointer bases, and error-correcting...
Zhang, Wenxian, Konstantinidis, N. P., Dobrovitski, V. V., Harmon, B. N., Santos, Lea F., Viola, Lorenza
The coherence time of an electron spin decohered by the nuclear spin environment in a quantum dot can be substantially increased by subjecting the electron to suitable dynamical decoupling sequences....
Quantum Chaos, Delocalization, and Entanglement in Disordered Heisenberg Models (2007)
Brown, Winton G., Santos, Lea F., Starling, David J., Viola, Lorenza
We investigate disordered one- and two-dimensional Heisenberg spin lattices across a transition from integrability to quantum chaos from both a statistical many-body and a quantum-information...
The structure of preserved information in quantum processes (2007)
Blume-Kohout, Robin, Ng, Hui Khoon, Poulin, David, Viola, Lorenza
We introduce a general operational characterization of information-preserving structures (IPS) -- encompassing noiseless subsystems, decoherence-free subspaces, pointer bases, and error-correcting...
Quantum Markovian Subsystems: Invariance, Attractivity, and Control (2007)
Ticozzi, Francesco, Viola, Lorenza
We characterize the dynamical behavior of continuous-time, Markovian quantum systems with respect to a subsystem of interest. Markovian dynamics describes a wide class of open quantum systems of...
Suppression of electron spin decoherence in a quantum dot (2007)
Zhang, Wenxian, Dobrovitski, V. V., Santos, Lea F., Viola, Lorenza, Harmon, B. N.
The dominant source of decoherence for an electron spin in a quantum dot is the hyperfine interaction with the surrounding bath of nuclear spins. The decoherence process may be slowed down by...
Viola, Lorenza, Brown, Winton G.
We establish contact between the delocalization properties of pure quantum states, as quantified by their number of principal components, and the average generalized entanglement properties, as...
Dynamical control of electron spin coherence in a quantum dot (2007)
Zhang, Wenxian, Dobrovitski, V. V., Santos, Lea F., Viola, Lorenza, Harmon, B. N.
We investigate the performance of dynamical decoupling methods at suppressing electron spin decoherence from a low-temperature nuclear spin reservoir in a quantum dot. The controlled dynamics is...
Entanglement and Subsystems, Entanglement beyond Subsystems, and All That (2007)
Viola, Lorenza, Barnum, Howard
Entanglement plays a pervasive role nowadays throughout quantum information science, and at the same time provides a bridging notion between quantum information science and fields as diverse as...
Single-bit Feedback and Quantum Dynamical Decoupling (2006)
Ticozzi, Francesco, Viola, Lorenza
Synthesizing an effective identity evolution in a target system subjected to unwanted unitary or non-unitary dynamics is a fundamental task for both quantum control and quantum information processing...
Generalized Coherent States as Preferred States of Open Quantum Systems (2006)
Boixo, Sergio, Viola, Lorenza, Ortiz, Gerardo
We investigate the connection between quasi-classical (pointer) states and generalized coherent states (GCSs) within an algebraic approach to Markovian quantum systems (including bosons, spins, and...
Generalized Entanglement as a Natural Framework for Exploring Quantum Chaos (2006)
Weinstein, Yaakov S., Viola, Lorenza
We demonstrate that generalized entanglement [Barnum {\em et al.}, Phys. Rev. A {\bf 68}, 032308 (2003)] provides a natural and reliable indicator of quantum chaotic behavior. Since generalized...
Enhanced Convergence and Robust Performance of Randomized Dynamical Decoupling (2006)
Santos, Lea F., Viola, Lorenza
We demonstrate the advantages of randomization in coherent quantum dynamical control. For systems which are either time-varying or require decoupling cycles involving a large number of operations, we...
Randomized Dynamical Decoupling Techniques for Coherent Quantum Control (2006)
Viola, Lorenza, Santos, Lea F.
The need for strategies able to accurately manipulate quantum dynamics is ubiquitous in quantum control and quantum information processing. We investigate two scenarios where randomized dynamical...
Randomized control of open quantum systems (2006)
The problem of open-loop dynamical control of generic open quantum systems is addressed. In particular, I focus on the task of effectively switching off environmental couplings responsible for...
Random decoupling schemes for quantum dynamical control and error suppression (2005)
Viola, Lorenza, Knill, Emanuel
We present a general control-theoretic framework for constructing and analyzing random decoupling schemes, applicable to quantum dynamical control of arbitrary finite-dimensional composite systems....
Dynamical control of qubit coherence: Random versus deterministic schemes (2005)
Santos, Lea F., Viola, Lorenza
We revisit the problem of switching off unwanted phase evolution and decoherence in a single two-state quantum system in the light of recent results on random dynamical decoupling methods [L. Viola...
Multipartite entanglement generation and fidelity decay in disordered qubit systems (2005)
Montangero, Simone, Viola, Lorenza
We investigate multipartite entanglement dynamics in disordered spin-1/2 lattice models exhibiting a transition from integrability to quantum chaos. Borrowing from the recently introduced generalized...
Barnum, Howard, Ortiz, Gerardo, Somma, Rolando, Viola, Lorenza
We define what it means for a state in a convex cone of states on a space of observables to be generalized-entangled relative to a subspace of the observables, in a general ordered linear spaces...
Experimental Implementation of a Concatenated Quantum Error-Correcting Code (2004)
Boulant, Nicolas, Viola, Lorenza, Fortunato, Evan M., Cory, David G.
Concatenated coding provides a general strategy to achieve the desired level of noise protection in quantum information storage and transmission. We report the implementation of a concatenated...
Advances in decoherence control (2004)
I address the current status of dynamical decoupling techniques in terms of required control resources and feasibility. Based on recent advances in both improving the theoretical design and assessing...
Entanglement as an Observer-Dependent Concept: An Application to Quantum Phase Transitions (2004)
Ortiz, Gerardo, Somma, Rolando, Barnum, Howard, Knill, Emanuel, Viola, Lorenza
This paper addresses the following main question: Do we have a theoretical understanding of entanglement applicable to a full variety of physical settings? It is clear that not only the assumption of...
Entanglement beyond subsystems (2004)
Viola, Lorenza, Barnum, Howard, Knill, Emanuel, Ortiz, Gerardo, Somma, Rolando
We present a notion of generalized entanglement which goes beyond the conventional definition based on quantum subsystems. This is accomplished by directly defining entanglement as a property of...
Nature and Measure of Entanglement in Quantum Phase Transitions (2004)
Somma, Rolando, Ortiz, Gerardo, Barnum, Howard, Knill, Emanuel, Viola, Lorenza
Characterizing and quantifying quantum correlations in states of many-particle systems is at the core of a full understanding of phase transitions in matter. In this work, we continue our...
Dynamical suppression of 1/f noise processes in qubit systems (2003)
We investigate the capability of dynamical decoupling techniques to reduce decoherence from a realistic environment generating 1/f noise. The predominance of low frequency modes in the noise profile...
A subsystem-independent generalization of entanglement (2003)
Barnum, Howard, Knill, Emanuel, Ortiz, Gerardo, Somma, Rolando, Viola, Lorenza
We introduce a generalization of entanglement based on the idea that entanglement is relative to a distinguished subspace of observables rather than a distinguished subsystem decomposition. A pure...
A note on verification procedures for quantum noiseless subsystems (2003)
Viola, Lorenza, Knill, Emanuel
We establish conditions under which the experimental verification of quantum error-correcting behavior against a linear set of error operators $\ce$ suffices for the verification of noiseless...
Contractive Schroedinger cat states for a free mass (2003)
Viola, Lorenza, Onofrio, Roberto
Contractive states for a free quantum particle were introduced by Yuen [Yuen H P 1983 Phys. Rev. Lett. 51, 719] in an attempt to evade the standard quantum limit for repeated position measurements....
Exploring Noiseless Subsystems via Nuclear Magnetic Resonance (2002)
Fortunato, Evan M., Viola, Lorenza, Pravia, Marco A., Knill, Emanuel, Laflamme, Raymond, Havel, Timothy F., ...
Noiseless subsystems offer a general and efficient method for protecting quantum information in the presence of noise that has symmetry properties. A paradigmatic class of error models displaying...
Robust dynamical decoupling with bounded controls (2002)
Viola, Lorenza, Knill, Emanuel
We propose a general procedure for implementing dynamical decoupling without requiring arbitrarily strong, impulsive control actions. This is accomplished by designing continuous decoupling...
Implementation of Universal Control on a Decoherence-Free Qubit (2001)
Fortunato, Evan M., Viola, Lorenza, Hodges, Jonathan, Teklemariam, Grum, Cory, David G.
We demonstrate storage and manipulation of one qubit encoded into a decoherence-free subspace (DFS) of two nuclear spins using liquid state nuclear magnetic resonance (NMR) techniques. The DFS is...
On Quantum Control via Encoded Dynamical Decoupling (2001)
I revisit the ideas underlying dynamical decoupling methods within the framework of quantum information processing, and examine their potential for direct implementations in terms of encoded rather...
NMR Quantum Information Processing and Entanglement (2001)
Laflamme, Raymond, Cory, David G., Negrevergne, Camille, Viola, Lorenza
In this essay we discuss the issue of quantum information and recent nuclear magnetic resonance (NMR) experiments. We explain why these experiments should be regarded as quantum information...
Constructing Qubits in Physical Systems (2001)
Viola, Lorenza, Knill, Emanuel, Laflamme, Raymond
The notion of a qubit is ubiquitous in quantum information processing. In spite of the simple abstract definition of qubits as two-state quantum systems, identifying qubits in physical systems is...
Havel, Timothy F., Sharf, Yehuda, Viola, Lorenza, Cory, David G.
An extension of the product operator formalism of NMR is introduced, which uses the Hadamard matrix product to describe many simple spin 1/2 relaxation processes. The utility of this formalism is...
Control of open quantum systems dynamics (2000)
We investigate the control resources needed to effect arbitrary quantum dynamics. We show that the ability to perform measurements on a quantum system, combined with the ability to feed back the...
Dynamical Generation of Noiseless Quantum Subsystems (2000)
Viola, Lorenza, Knill, Emanuel, Lloyd, Seth
We present control schemes for open quantum systems that combine decoupling and universal control methods with coding procedures. By exploiting a general algebraic approach, we show how appropriate...
Microwave study of quantum n-disk scattering (1999)
Lu, Wentao, Viola, Lorenza, Pance, Kristi, Rose, Michael, Sridhar, S.
We describe a wave-mechanical implementation of classically chaotic n-disk scattering based on thin 2-D microwave cavities. Two, three, and four-disk scattering are investigated in detail. The...
Theory of Quantum Error Correction for General Noise (1999)
Knill, Emanuel, Laflamme, Raymond, Viola, Lorenza
Quantum error correction protects quantum information against environmental noise. When using qubits, a measure of quality of a code is the maximum number of errors that it is able to correct. We...
Universal Control of Decoupled Quantum Systems (1999)
Viola, Lorenza, Lloyd, Seth, Knill, Emanuel
It is shown that if one can perform a restricted set of fast manipulations on a quantum system, one can implement a large class of dynamical evolutions by effectively removing or introducing selected...
Tunneling Proximity Resonances: Interplay between Symmetry and Dissipation (1999)
Pance, Kristi, Viola, Lorenza, Sridhar, S.
We report the first observation of bound-state proximity resonances in coupled dielectric resonators. The proximity resonances arise from the combined action of symmetry and dissipation. We argue...
Dynamical Decoupling of Open Quantum Systems (1998)
Viola, Lorenza, Knill, Emanuel, Lloyd, Seth
We propose a novel dynamical method for beating decoherence and dissipation in open quantum systems. We demonstrate the possibility of filtering out the effects of unwanted (not necessarily known)...
Decoherence control in quantum information processing: simple models (1998)
We explore a strategy for protecting the evolution of a qubit against the effects of environmental noise based on the application of controlled time-dependent perturbations. In the case of a purely...
Dynamics of decoherence in continuous atom-optical quantum nondemolition measurements (1998)
Onofrio, Roberto, Viola, Lorenza
The Lindblad approach to continuous quantum measurements is applied to a system composed of a two-level atom interacting with a stationary quantized electromagnetic field through a dispersive...
Dynamical suppression of decoherence in two-state quantum systems (1998)
The dynamics of a decohering two-level system driven by a suitable control Hamiltonian is studied. The control procedure is implemented as a sequence of radiofrequency pulses that repetitively flip...
Quantum Phenomenology with the Path Integral Approach (1997)
Calarco, Tommaso, Onofrio, Roberto, Presilla, Carlo, Viola, Lorenza
A quantum measurement model based upon restricted path-integrals allows us to study measurements of generalized position in various one-dimensional systems of phenomenological interest. After a...
Gravitation at the mesoscopic scale (1997)
Onofrio, Roberto, Viola, Lorenza
Free fall experiments are discussed by using test masses associated to quantum states not necessarily possessing a classical counterpart. The times of flight of the Galileian experiments using...
Lindblad Approach to Nonlinear Jaynes-Cummings Dynamics of a Trapped Ion (1997)
Onofrio, Roberto, Viola, Lorenza
The Lindblad approach to open quantum systems is introduced for studying the dynamics of a single trapped ion prepared in nonclassical motional states and subjected to continuous measurement of its...
Measured Quantum Dynamics of a Trapped Ion (1997)
Viola, Lorenza, Onofrio, Roberto
The measurement process is taken into account in the dynamics of trapped ions prepared in nonclassical motional states. The induced decoherence is shown to manifest itself both in the inhibition of...
Macroscopic quantum damping in SQUID rings (1997)
Viola, Lorenza, Onofrio, Roberto, Calarco, Tommaso
The measurement process is introduced in the dynamics of Josephson devices exhibiting quantum behaviour in a macroscopic degree of freedom. The measurement is shown to give rise to a dynamical...
Testing the equivalence principle through freely falling quantum objects (1996)
Viola, Lorenza, Onofrio, Roberto
Free fall in a uniform gravitational field is revisited in the case of quantum states with and without classical analogue. The interplay between kinematics and dynamics in the evolution of a falling...
Quantum damping of position due to energy measurements (1996)
Onofrio, Roberto, Viola, Lorenza
Quantum theory for measurements of energy is introduced and its consequences for the average position of monitored dynamical systems are analyzed. It turns out that energy measurements lead to a...
Morato, Laura M., Viola, Lorenza
We revisit the classical approach of comoving coordinates in relativistic hydrodynamics and we give a constructive proof for their global existence under suitable conditions which is proper for...