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See detailArtificial Abelian gauge potentials induced by dipole-dipole interactions between Rydberg atoms
Cesa, Alexandre ULg; Martin, John ULg

Poster (2014, March 19)

We analyze the influence of dipole-dipole interactions between Rydberg atoms on the generation of Abelian artificial gauge potentials and fields. When two Rydberg atoms are driven by a uniform laser field ... [more ▼]

We analyze the influence of dipole-dipole interactions between Rydberg atoms on the generation of Abelian artificial gauge potentials and fields. When two Rydberg atoms are driven by a uniform laser field, we show that the combined atom-atom and atom-field interactions give rise to nonuniform, artificial gauge potentials. We identify the mechanism responsible for the emergence of these gauge potentials. Analytical expressions for the latter indicate that the strongest artificial magnetic fields are reached in the regime intermediate between the dipole blockade regime and the regime in which the atoms are sufficiently far apart such that atom-light interaction dominates over atom-atom interactions. We discuss the differences and similarities of artificial gauge fields originating from resonant dipole-dipole and van der Waals interactions. We also give an estimation of experimentally attainable artificial magnetic fields resulting from this mechanism and we discuss their detection through the deflection of the atomic motion. [less ▲]

Detailed reference viewed: 15 (7 ULg)
See detailInfluence of dipole-dipole interactions decoherence-free states
Damanet, François ULg; Martin, John ULg

Poster (2014, March 18)

Decoherence, known as the consequence of the coupling of any quan- tum system to its environment, causes information loss in the system and represents a major problem in the physical realization of quan ... [more ▼]

Decoherence, known as the consequence of the coupling of any quan- tum system to its environment, causes information loss in the system and represents a major problem in the physical realization of quan- tum computers [1]. Decoherence-Free States (DFS) are considered as a possible solution to this problem. A set of trapped cold atoms placed in a DFS state will be immune against decoherence due to sponta- neous emission. However, because of dipole-dipole interactions between atoms, induced dephasing effects are likely to destroy the coherence and drive the system out of its DFS [1-2]. In this work, we study nu- merically the dynamics of a set of two-level atoms initially in a DFS with respect to dissipative processes by solving the master equation in- cluding both dissipative dynamics and dipole dipole interactions. We focus our attention on the influence of dipolar coupling on the radiated energy rate and coherence of the system as in [3]. In particular, by av- eraging over many realizations of close randomly distributed atomic positions, we show the formation of a superradiant-like pulse and we study its properties as a function of the dipolar coupling strength. [1] D. A. Lidar & K. B. Whaley, Lectures Notes in Phys., Vol. 622, p83-120, Springer (2003). [2] M. Gross & S. Haroche, Physics reports 93, 301-396 (1982). [3] W. Feng, Y. Li & S. -Y. Zhu, arXiv :1302.0957. (2013). [less ▲]

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See detailOn the Identication of Symmetric N-qubit Maximally Entangled States
Baguette, Dorian ULg; Bastin, Thierry ULg; Martin, John ULg

Poster (2014, March 11)

Maximally entangled states can serve as a useful resource in many different contexts. It is therefore important to identify those states. Here we are interested in the identification of maximally ... [more ▼]

Maximally entangled states can serve as a useful resource in many different contexts. It is therefore important to identify those states. Here we are interested in the identification of maximally entangled states in the symmetric subspace of an N-qubit system. By maximally entangled states, we refer to symmetric states characterized by a one qubit reduced density matrix proportional to the identity. These states maximise various entanglement measures [1] such as von Neumann and Meyer-Wallach entropy and are unique up to LU in their SLOCC class [2]. We identify and characterize all maximally entangled symmetric states up to 4 qubits. We provide general conditions for a symmetric state with an arbitrary number of qubits to be maximally entangled and identify families of SLOCC classes which do not contain any maximally entangled states. [1] F. Verstraete, J. Dehaene, B. De Moor, Phys. Rev. A 68, 012103 (2003). [2] G. Gour, N. Wallach, N. J. Phys. 13, 073013 (2011) [less ▲]

Detailed reference viewed: 25 (3 ULg)
See detailHighly non-classical symmetric states of an N-qubit system
Baguette, Dorian ULg; Martin, John ULg

Poster (2013, September 02)

In this work, we consider two measures of non-classicality for pure symmetric N-qubit states : Wehrl entropy (S) and Wehrl participation ratio (R). Measures of non-classicality help to the understanding ... [more ▼]

In this work, we consider two measures of non-classicality for pure symmetric N-qubit states : Wehrl entropy (S) and Wehrl participation ratio (R). Measures of non-classicality help to the understanding of the mechanisms responsible for the transition from quantum to classical physics and are usefull in the context of information processing and quantum-enhanced measurements. [less ▲]

Detailed reference viewed: 25 (6 ULg)
See detailInfluence of dipole-dipole interactions on superradiance
Damanet, François ULg; Martin, John ULg

Poster (2013, September 02)

Superradiance, known as the cooperative spontaneous emission of a directional light pulse by excited atoms placed in vacuum, has recently regained attention in the context of photon localization [1] and ... [more ▼]

Superradiance, known as the cooperative spontaneous emission of a directional light pulse by excited atoms placed in vacuum, has recently regained attention in the context of photon localization [1] and single photon cooperative emission [2]. The dissipative dynamics of the atoms is known to depend dramatically on the ratio between the typical inter- atomic distance and the atomic transition wavelength, notably because of dipole-dipole interactions [3]. In this work, we study the effects of these interactions on superradiance as in [4] by solving numerically the corresponding master equation. In particular, by averaging over many realizations of the randomly distributed atomic positions, we show that the decay of the radiated energy pulse height with the intensity of the dipolar coupling follows a power law. [1] E. Ackermans, A. Gero & R. Kaiser, Phys. Rev. Lett. 101, 103602 (2008). [2] R. Friedberg & J. T. Manassah, J. Phys. B 43, 035501 (2010). [3] M. Gross & S. Haroche, Physics reports 93, 301-396 (1982). [4] B. Coffey & R. Friedberg, Phys. Rev. A 17, 1033 (1978). [less ▲]

Detailed reference viewed: 36 (5 ULg)
See detailMultifractality of quantum wave functions
Dubertrand, Rémy; Garcia-Mata, Ignacio; Georgeot, Bertrand et al

Poster (2013, September)

Detailed reference viewed: 20 (1 ULg)
See detailInfluence of dipole-dipole interactions on the superradiant pulse
Damanet, François ULg; Martin, John ULg

Poster (2013, May 23)

Superradiance, known as the cooperative spontaneous emission of a directional light pulse by excited atoms placed in vacuum, has recently regained attention in the context of photon localization [1] and ... [more ▼]

Superradiance, known as the cooperative spontaneous emission of a directional light pulse by excited atoms placed in vacuum, has recently regained attention in the context of photon localization [1] and single photon cooperative emission [2]. The dissipative dynamics of the atoms is known to depend dramatically on the ratio between the typical inter-atomic distance and the atomic transition wavelength, notably because of dipole-dipole interactions [3]. In this work, we study the effects of these interactions on superradiance as in [4] by solving numerically the corresponding master equation. In particular, by averaging over many realizations of the randomly distributed atomic positions, we show that the decay of the radiated energy pulse height with the intensity of the dipolar coupling follows a power law. [1] E. Ackermans, A. Gero & R. Kaiser, Phys. Rev. Lett. 101, 103602 (2008). [2] R. Friedberg & J. T. Manassah, J. Phys. B 43, 035501 (2010). [3] M. Gross & S. Haroche, Physics reports 93, 301-396 (1982). [4] B. Coffey & R. Friedberg, Phys. Rev. A 17, 1033 (1978). [less ▲]

Detailed reference viewed: 17 (4 ULg)
See detailThe most non-classical symmetric states of an N-qubit system
Baguette, Dorian ULg; Martin, John ULg

Poster (2013, May 23)

Detailed reference viewed: 25 (3 ULg)
See detailWeakening of superradiance due to dipole-dipole interactions
Damanet, François ULg; Martin, John ULg

Poster (2013, March 19)

Detailed reference viewed: 23 (13 ULg)
See detailHighly non-classical symmetric states of an N-qubit system
Baguette, Dorian ULg; Martin, John ULg

Poster (2013, March 19)

Detailed reference viewed: 20 (8 ULg)
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See detailMultifractality of quantum wave functions
Martin, John ULg; Garcia-Mata, Ignacio; Giraud, Olivier et al

Poster (2013, March 19)

We study the multifractality of individual wave packets in a periodically kicked system through a combination of numerical and analytical works. We consider a version of the mathematical Ruijsenaars ... [more ▼]

We study the multifractality of individual wave packets in a periodically kicked system through a combination of numerical and analytical works. We consider a version of the mathematical Ruijsenaars-Schneider model and reinterpreted it physically in order to describe the spreading with time of quantum wave packets in a system where multifractality can be tuned by varying a parameter [1]. We compare different methods to measure the multifractality of wave packets and identify the best one. We find the multifractality to decrease with time until it reaches an asymptotic limit, which is different from the multifractality of eigenvectors but related to it, as is the rate of the decrease. Our results could guide the study of experimental situations where multifractality is present in quantum systems. [less ▲]

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See detailAdenovirus-mediated gene therapy with sitimagene ceradenovec followed by intravenous ganciclovir for patients with operable high-grade glioma (ASPECT): a randomised, open-label, phase 3 trial.
Westphal, Manfred; Yla-Herttuala, Seppo; Martin, John ULg et al

in The lancet oncology (2013), 14(9), 823-33

BACKGROUND: Besides the use of temozolomide and radiotherapy for patients with favourable methylation status, little progress has been made in the treatment of adult glioblastoma. Local control of the ... [more ▼]

BACKGROUND: Besides the use of temozolomide and radiotherapy for patients with favourable methylation status, little progress has been made in the treatment of adult glioblastoma. Local control of the disease by complete removal increases time to progression and survival. We assessed the efficacy and safety of a locally applied adenovirus-mediated gene therapy with a prodrug converting enzyme (herpes-simplex-virus thymidine kinase; sitimagene ceradenovec) followed by intravenous ganciclovir in patients with newly diagnosed resectable glioblastoma. METHODS: For this international, open-label, randomised, parallel group multicentre phase 3 clinical trial, we recruited patients from 38 sites in Europe. Patients were eligible if they were aged 18-70 years, had newly diagnosed supratentorial glioblastoma multiforme amenable to complete resection, and had a Karnofsky score of 70 or more at screening. We used a computer-generated randomisation sequence to allocate patients in a one-to-one ratio (with block sizes of four) to receive either surgical resection of the tumour and intraoperative perilesional injection of sitimagene ceradenovec (1 x 10(12) viral particles) followed by ganciclovir (postoperatively, 5 mg/kg intravenously twice a day) in addition to standard care or resection and standard care alone. Temozolomide, not being standard in all participating countries at the time of the study, was allowed at the discretion of the treating physician. The primary endpoint was a composite of time to death or re-intervention, adjusted for temozolamide use, assessed by intention-to-treat (ITT) analysis. This trial is registered with EudraCT, number 2004-000464-28. FINDINGS: Between Nov 3, 2005, and April 16, 2007, 250 patients were recruited and randomly allocated: 124 to the experimental group and 126 to the standard care group, of whom 119 and 117 patients, respectively, were included in the ITT analyses. Median time to death or re-intervention was longer in the experimental group (308 days, 95% CI 283-373) than in the control group (268 days, 210-313; hazard ratio [HR] 1.53, 95% CI 1.13-2.07; p=0.006). In a subgroup of patients with non-methylated MGMT, the HR was 1.72 (95% CI 1.15-2.56; p=0.008). However, there was no difference between groups in terms of overall survival (median 497 days, 95% CI 369-574 for the experimental group vs 452 days, 95% CI 437-558 for the control group; HR 1.18, 95% CI 0.86-1.61, p=0.31). More patients in the experimental group had one or more treatment-related adverse events those in the control group (88 [71%] vs 51 [43%]). The most common grade 3-4 adverse events were hemiparesis (eight in the experimental group vs three in the control group) and aphasia (six vs two). INTERPRETATION: Our findings suggest that use of sitimagene ceradenovec and ganciclovir after resection can increase time to death or re-intervention in patients with newly diagnosed supratentorial glioblastoma multiforme, although the intervention did not improve overall survival. Locally delivered gene therapy for glioblastoma should be further developed, especially for patients who are unlikely to respond to standard chemotherapy. FUNDING: Ark Therapeutics Ltd. [less ▲]

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See detailArtificial Abelian gauge potentials induced by dipole-dipole interactions between Rydberg atoms
Cesa, Alexandre; Martin, John ULg

in Physical Review. A (2013), 88

We analyze the influence of dipole-dipole interactions between Rydberg atoms on the generation of Abelian artificial gauge potentials and fields. When two Rydberg atoms are driven by a uniform laser field ... [more ▼]

We analyze the influence of dipole-dipole interactions between Rydberg atoms on the generation of Abelian artificial gauge potentials and fields. When two Rydberg atoms are driven by a uniform laser field, we show that the combined atom-atom and atom-field interactions give rise to new, nonuniform, artificial gauge potentials. We identify the mechanism responsible for the emergence of these gauge potentials. Analytical expressions for the latter indicate that the strongest artificial magnetic fields are reached in the regime intermediate between the dipole blockade regime and the regime in which the atoms are sufficiently far apart such that atom-light interaction dominates over atom-atom interactions. We discuss the differences and similarities of artificial gauge fields originating from resonant dipole-dipole and van der Waals interactions. We also give an estimation of experimentally attainable artificial magnetic fields resulting from this mechanism and we discuss their detection through the deflection of the atomic motion. [less ▲]

Detailed reference viewed: 46 (16 ULg)
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See detailMultifractality of quantum wave packets
Garcia-Mata, Ignacio; Martin, John ULg; Giraud, Olivier et al

in Physical Review. E : Statistical, Nonlinear, and Soft Matter Physics (2012), 86

We study a version of the mathematical Ruijsenaars-Schneider model and reinterpret it physically in order to describe the spreading with time of quantum wave packets in a system where multifractality can ... [more ▼]

We study a version of the mathematical Ruijsenaars-Schneider model and reinterpret it physically in order to describe the spreading with time of quantum wave packets in a system where multifractality can be tuned by varying a parameter. We compare different methods to measure the multifractality of wave packets and identify the best one. We find the multifractality to decrease with time until it reaches an asymptotic limit, which is different from the multifractality of eigenvectors but related to it, as is the rate of the decrease. Our results could guide the study of experimental situations where multifractality is present in quantum systems. [less ▲]

Detailed reference viewed: 52 (3 ULg)
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See detailThe quest for highly entangled symmetric states
Martin, John ULg

Scientific conference (2012, June 05)

Detailed reference viewed: 21 (10 ULg)
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See detailHeisenberg-limited Metrology without Entanglement
Braun, Daniel; Martin, John ULg

in Research in Optical Sciences, OSA Technical Digest (2012)

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See detailHeisenberg-limited metrology without entanglement
Braun, Daniel; Martin, John ULg

Conference (2012, March)

Detailed reference viewed: 7 (0 ULg)
See detailHeisenberg-limited metrology without entanglement
Braun, Daniel; Martin, John ULg

Conference (2012, January)

Detailed reference viewed: 5 (1 ULg)
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See detailMultiqubit symmetric states with a high geometric entanglement
Martin, John ULg; Giraud, Olivier; Braun, Peter et al

Poster (2011, May 25)

We propose a detailed study of the geometric entanglement properties of pure symmetric N-qubit states, focusing more particularly on the identification of symmetric states with a high geometric ... [more ▼]

We propose a detailed study of the geometric entanglement properties of pure symmetric N-qubit states, focusing more particularly on the identification of symmetric states with a high geometric entanglement and how their entanglement behaves asymptotically for large N. We show that much higher geometric entanglement with improved asymptotical behavior can be obtained in comparison with the highly entangled balanced Dicke states studied previously. We also derive an upper bound for the geometric measure of entanglement of symmetric states. The connection with the quantumness of a state is discussed. [less ▲]

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See detailHeisenberg-limited sensitivity with decoherence-enhanced measurements
Braun, D.; Martin, John ULg

in Nature Communications (2011), 2(223), 1-9

Quantum-enhanced measurements use quantum mechanical effects to enhance the sensitivity of the measurement of classical quantities, such as the length of an optical cavity. The major goal is to beat the ... [more ▼]

Quantum-enhanced measurements use quantum mechanical effects to enhance the sensitivity of the measurement of classical quantities, such as the length of an optical cavity. The major goal is to beat the standard quantum limit (SQL), that is, an uncertainty of order 1/ N, where N is the number of quantum resources (for example, the number of photons or atoms used), and to achieve a scaling 1/N, known as the Heisenberg limit. So far very few experiments have demonstrated an improvement over the SQL. The required quantum states are generally highly entangled, difficult to produce, and very prone to decoherence. Here, we show that Heisenberg- limited measurements can be achieved without the use of entangled states by coupling the quantum resources to a common environment that can be measured at least in part. The method is robust under decoherence, and in fact the parameter dependence of collective decoherence itself can be used to reach a 1/N scaling. [less ▲]

Detailed reference viewed: 68 (24 ULg)