05.70.+o Quantum information & quantum control

Implementation of an experimentally feasible controlled-phase gate on two blockaded Rydberg atoms

Date: 
2014-03-28 - 2014-11-27
Author(s): 

M. M. Müller, M Murphy, S Montangero, T Calarco, P Grangier, A Browaeys

Reference: 

Journal reference: Phys. Rev. A 89, 032334 (2014)
DOI: 10.1103/PhysRevA.89.032334

We investigate the implementation of a controlled-Z gate on a pair of Rydberg atoms in spatially separated dipole traps where the joint excitation of both atoms into the Rydberg level is strongly suppressed (the Rydberg blockade). We follow the adiabatic gate scheme of Jaksch et al.

Fast quantum gate via Feshbach-Pauli blocking in a nanoplasmonic trap

Date: 
2014-06-25 - 2014-11-27
Author(s): 

K. Jachymski, Z. Idziaszek, T. Calarco

Reference: 

DOI: 10.1103/PhysRevLett.112.250502
Journal reference: Phys. Rev. Lett. 112, 250502 (2014)

We propose a simple idea for realizing a quantum gate with two identical fermions in a double well trap via external optical pulses without addressing the atoms individually. The key components of the scheme are Feshbach resonance and Pauli blocking, which decouple unwanted states from the dynamics.

Optimal preparation of quantum states on an atom chip device

Date: 
2014-05-27 - 2014-11-27
Author(s): 

C. Lovecchio, F Schäfer, S Cherukattil, A K Murtaza, I Herrera, F S Cataliotti, T Calarco, S Montangero, F Caruso

Reference: 

arXiv:1405.6918

Atom chips provide compact and robust platforms towards practical quantum technologies. A quick and faithful preparation of arbitrary input states for these systems is crucial but represents a very challenging experimental task. This is especially difficult when the dynamical evolution is noisy and unavoidable setup imperfections have to be considered.

Noise-resistant optimal spin squeezing via quantum control

Date: 
2014-04-26 - 2014-11-27
Author(s): 

T. Caneva, S. Montangero, M. D. Lukin, T. Calarco

Reference: 

arXiv:1304.7195v2

Entangled atomic states, such as spin squeezed states, represent a promising resource for a new generation of quantum sensors and atomic clocks. We demonstrate that optimal control techniques can be used to substantially enhance the degree of spin squeezing in strongly interacting many-body systems, even in the presence of noise and imperfections.

Tuning heat transport in trapped-ion chains across a structural phase transition

Date: 
2014-01-25
Author(s): 

Antonia Ruiz, Daniel Alonso, Martin B. Plenio and Adolfo del Campo

Reference: 

arXiv:1401.5480

We explore heat transport across an ion Coulomb crystal beyond the harmonic regime by tuning it across the structural phase transition between the linear and zigzag configurations. This demonstrates that the control of the spatial ion distribution by varying the trapping frequencies renders ion Coulomb crystals an ideal test-bed to study heat transport properties in finite open system of tunable non-linearities.

High fidelity spin entanglement using optimal control

Date: 
2014-02-28
Author(s): 

F. Dolde, V. Bergholm, Y. Wang, I. Jakobi, S. Pezzagna, J. Meijer, P. Neumann, T. Schulte-Herbrueggen, J. Biamonte, and J. Wrachtrup

Reference: 

Nature Communications 5, 3371 (2014)

Precise control of quantum systems is of fundamental importance in quantum information processing, quantum metrology and high-resolution spectroscopy. When scaling up quantum registers, several challenges arise: individual addressing of qubits while suppressing cross-talk, entangling distant nodes and decoupling unwanted interactions. Here we experimentally demonstrate optimal control of a prototype spin qubit system consisting of two proximal nitrogen-vacancy centres in diamond. Using engineered microwave pulses, we demonstrate single electron spin operations with a fidelity F≈0.99.

Realistic and verifiable coherent control of excitonic states in a light harvesting complex

Date: 
2013-07-19
Author(s): 

Filippo Caruso, Simone Montangero, Mohan Sarovar, Tommaso Calarco, Martin B. Plenio, K. Birgitta Whaley,
Stephan Hoyer

Reference: 

arXiv:1307.4807v1

We explore the feasibility of coherent control of excitonic dynamics in light harvesting complexes despite the open nature of these quantum systems. We establish feasible targets for phase and phase/amplitude control of the electronically excited state populations in the Fenna-Mathews-Olson (FMO) complex and analyze the robustness of this control.

Control of inhomogeneous atomic ensembles of hyperfine qudits

Date: 
2012-02-03
Author(s): 

Brian E. Mischuck, Seth T. Merkel, and Ivan H. Deutsch

Reference: 

URL: http://link.aps.org/doi/10.1103/PhysRevA.85.022302
DOI: 10.1103/PhysRevA.85.022302
PACS: 03.67.Lx, 42.50.Dv, 32.80.Qk

We study the ability to control d-dimensional quantum systems (qudits) encoded in the hyperfine spin of alkali-metal atoms through the application of radio- and microwave-frequency magnetic fields in the presence of inhomogeneities in amplitude and detuning. Such a capability is essential to the design of robust pulses that mitigate the effects of experimental uncertainty and also for application to tomographic addressing of particular members of an extended ensemble. We study the problem of preparing an arbitrary state in the Hilbert space from an initial fiducial state.

High-fidelity quantum driving

Date: 
2011-12-18
Author(s): 

M. G. Bason, M. Viteau, N. Malossi, P. Huillery, E. Arimondo, D. Ciampini, R. Fazio, V. Giovannetti, R. Mannella, and O. Morsch

Reference: 

Nature Phys. 8, 147-152 (2012)

Accurately controlling a quantum system is a fundamental requirement in quantum information processing and the coherent manipulation of molecular systems. The ultimate goal in quantum control is to prepare a desired state with the highest fidelity allowed by the available resources and the experimental constraints. Here we experimentally implement two optimal high-fidelity control protocols using a two-level quantum system comprising Bose–Einstein condensates in optical lattices.

Control of inhomogeneous atomic ensembles of hyperfine qudits

Date: 
2011-09-01
Author(s): 

Brian E. Mischuck, Seth T. Merkel, and Ivan H. Deutsch

Reference: 

arXiv:1109.0146v1

We study the ability to control d-dimensional quantum systems (qudits) encoded in the hyperfine spin of alkali-metal atoms through the application of radio- and microwave-frequency magnetic fields in the presence of inhomogeneities in amplitude and detuning. Such a capability is essential to the design of robust pulses that mitigate the effects of experimental uncertainty and also for application to tomographic addressing of particular members of an extended ensemble. We study the problem of preparing an arbitrary state in the Hilbert space from an initial fiducial state.

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