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Results 1-20 of 22.
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Non-Hermitian Hamiltonian deformations in quantum mechanics Matsoukas, Stylianos-Apollonas ; Roccati, Federico ; Cornelius, Julien Marion et al in Journal of High Energy Physics (2023), 01(60), Detailed reference viewed: 44 (0 UL)Analyticity constraints bound the decay of the spectral form factor Chenu, Aurélia ; Martinez Azcona, Pablo in Quantum (2022) Detailed reference viewed: 27 (0 UL)Spectral Filtering Induced by Non-Hermitian Evolution with Balanced Gain and Loss: Enhancing Quantum Chaos Chenu, Aurélia ; Del Campo Echevarria, Adolfo ; et al in Physical Review Letters (2022) Detailed reference viewed: 37 (2 UL)From hybrid polariton to dipolariton using non-Hermitian Hamiltonians to handle particle lifetimes Chenu, Aurélia ; ; et al in Physical Review. B, Condensed Matter (2022) We consider photons strongly coupled to the excitonic excitations of a coupled quantum well, in the presence of an electric field. We show how, under a field increase, the hybrid polariton made of a ... [more ▼] We consider photons strongly coupled to the excitonic excitations of a coupled quantum well, in the presence of an electric field. We show how, under a field increase, the hybrid polariton made of a photon coupled to hybrid carriers lying in the two wells transforms into a dipolariton made of a photon coupled to direct and indirect excitons. We also show how the cavity photon lifetime and the coherence time of the carrier wave vectors that we analytically handle through non-hermitian Hamiltonians affect these polaritonic states. While the hybrid polaritons display a spectral singularity where the eigenvalues coalesce, known as an exceptional point, that depends on detuning and lifetimes, we find that the three dipolaritonic states display an anticrossing without exceptional point due to the interaction between photons, direct, and indirect excitons. [less ▲] Detailed reference viewed: 45 (3 UL)Entropy-based formulation of thermodynamics in arbitrary quantum evolution ; ; Chenu, Aurélia et al in Physical Review A (2022) Given the evolution of an arbitrary open quantum system, we formulate a general and unambiguous method to separate the internal energy change of the system into an entropy-related contribution and a part ... [more ▼] Given the evolution of an arbitrary open quantum system, we formulate a general and unambiguous method to separate the internal energy change of the system into an entropy-related contribution and a part causing no entropy change, identified as heat and work, respectively. We also demonstrate that heat and work admit geometric and dynamical descriptions by developing a universal dynamical equation for the given trajectory of the system. The dissipative and coherent parts of this equation contribute exclusively to heat and work, where the specific role of a work contribution from a counterdiabatic drive is underlined. Next we define an expression for the irreversible entropy production of the system which does not have explicit dependence on the properties of the ambient environment; rather, it depends on a set of the system's observables excluding its Hamiltonian and is independent of internal energy change. We illustrate our results with three examples. [less ▲] Detailed reference viewed: 75 (4 UL)Shortcuts to Squeezed Thermal States Dupays, Léonce ; Chenu, Aurélia in Quantum (2021) Squeezed state in harmonic systems can be generated through a variety of techniques, including varying the oscillator frequency or using nonlinear two-photon Raman interaction. We focus on these two ... [more ▼] Squeezed state in harmonic systems can be generated through a variety of techniques, including varying the oscillator frequency or using nonlinear two-photon Raman interaction. We focus on these two techniques to drive an initial thermal state into a final squeezed thermal state with controlled squeezing parameters—amplitude and phase—in arbitrary time. The protocols are designed through reverse engineering for both unitary and open dynamics. Control of the dissipation is achieved using stochastic processes, readily implementable via, e.g., continuous quantum measurements. Importantly, this allows controlling the state entropy and can be used for fast thermalization. The developed protocols are thus suited to generate squeezed thermal states at controlled temperature in arbitrary time. [less ▲] Detailed reference viewed: 71 (3 UL)Thermofield dynamics: Quantum chaos versus decoherence ; Chenu, Aurélia ; et al in Physical Review. B, Condensed Matter and Materials Physics (2021) Quantum chaos imposes universal spectral signatures that govern the thermofield dynamics of a many-body system in isolation. The fidelity between the initial and time-evolving thermofield double states ... [more ▼] Quantum chaos imposes universal spectral signatures that govern the thermofield dynamics of a many-body system in isolation. The fidelity between the initial and time-evolving thermofield double states exhibits as a function of time a decay, dip, ramp, and plateau. Sources of decoherence give rise to a nonunitary evolution and result in information loss. Energy dephasing gradually suppresses quantum noise fluctuations and the dip associated with spectral correlations. Decoherence further delays the appearance of the dip and shortens the span of the linear ramp associated with chaotic behavior. The interplay between signatures of quantum chaos and information loss is determined by the competition among the decoherence, dip, and plateau characteristic times, as demonstrated in the stochastic Sachdev-Ye-Kitaev model. [less ▲] Detailed reference viewed: 64 (3 UL)First law of quantum thermodynamics in a driven open two-level system ; Chenu, Aurélia in Physical Review. A (2021) Assigning the variations of internal energy into heat or work contributions is a challenging task due to the fact that these properties are trajectory dependent. A number of proposals have been put ... [more ▼] Assigning the variations of internal energy into heat or work contributions is a challenging task due to the fact that these properties are trajectory dependent. A number of proposals have been put forward for open quantum systems following an arbitrary dynamics. We here focus on nonequilibrium thermodynamics of a two-level system and explore in addition to the conventional approach, two definitions motivated by either classical work or heat in which the driving Hamiltonian or the trajectory itself, respectively, are used to set up a reference basis. We first give the thermodynamic properties for an arbitrary dynamics and illustrate the results on the Bloch sphere. Then, we solve the particular example of a periodically driven qubit interacting with a dissipative and decoherence bath. Our results illustrate the trajectory-dependent character of heat and work and how contributions originally assigned to dissipation in the Lindblad equation can become a coherent part assigned to work. [less ▲] Detailed reference viewed: 60 (2 UL)Superadiabatic thermalization of a quantum oscillator by engineered dephasing Dupays, Léonce ; ; Del Campo Echevarria, Adolfo et al in Physical Review Research (2020), 2 Fast nonadiabatic control protocols known as shortcuts to adiabaticity have found a plethora of applications, but their use has been severely limited to speeding up the dynamics of isolated quantum ... [more ▼] Fast nonadiabatic control protocols known as shortcuts to adiabaticity have found a plethora of applications, but their use has been severely limited to speeding up the dynamics of isolated quantum systems. We introduce shortcuts for open quantum processes that make possible the fast control of Gaussian states in nonunitary processes. Specifically, we provide the time modulation of the trap frequency and dephasing strength that allow preparing an arbitrary thermal state in a finite time. Experimental implementation can be done via stochastic parametric driving or continuous measurements, readily accessible in a variety of platforms. [less ▲] Detailed reference viewed: 41 (3 UL)Shortcuts to Adiabaticity in Driven Open Quantum Systems: Balanced Gain and Loss and Non-Markovian Evolution ; Chenu, Aurélia ; et al in Quantum (2020), 4 A universal scheme is introduced to speed up the dynamics of a driven open quantum system along a prescribed trajectory of interest. This framework generalizes counterdiabatic driving to open quantum ... [more ▼] A universal scheme is introduced to speed up the dynamics of a driven open quantum system along a prescribed trajectory of interest. This framework generalizes counterdiabatic driving to open quantum processes. Shortcuts to adiabaticity designed in this fashion can be implemented in two alternative physical scenarios: one characterized by the pres- ence of balanced gain and loss, the other involves non-Markovian dynamics with time-dependent Lindblad operators. As an illustration, we engineer superadiabatic cooling, heating, and isothermal strokes for a two-level system, and provide a pro- tocol for the fast thermalization of a quantum oscillator. [less ▲] Detailed reference viewed: 39 (1 UL)Comparison of the Energy-Transfer Rates in Structural and Spectral Variants of the B800–850 Complex from Purple Bacteria ; ; et al in Journal of Physical Chemistry B (2020), 124 Photosynthetic light harvesting can occur with a remarkable near-unity quantum efficiency. The B800–850 complex, also known as light-harvesting complex 2 (LH2), is the primary light-harvesting complex in ... [more ▼] Photosynthetic light harvesting can occur with a remarkable near-unity quantum efficiency. The B800–850 complex, also known as light-harvesting complex 2 (LH2), is the primary light-harvesting complex in purple bacteria and has been extensively studied as a model system. The bacteriochlorophylls of the B800–850 complex are organized into two concentric rings, known as the B800 and B850 rings. However, depending on the species and growth conditions, the number of constituent subunits, the pigment geometry, and the absorption energies vary. While the dynamics of some B800–850 variants have been exhaustively characterized, others have not been measured. Furthermore, a direct and simultaneous comparison of how both structural and spectral differences between variants affect these dynamics has not been performed. In this work, we utilize ultrafast transient absorption measurements to compare the B800 to B850 energy-transfer rates in the B800–850 complex as a function of the number of subunits, geometry, and absorption energies. The nonameric B800–850 complex from Rhodobacter (Rb.) sphaeroides is 40% faster than the octameric B800–850 complex from Rhodospirillum (Rs.) molischianum, consistent with structure-based predictions. In contrast, the blue-shifted B800–820 complex from Rs. molischianum is only 20% faster than the B800–850 complex from Rs. molischianum despite an increase in the spectral overlap between the rings that would be expected to produce a larger increase in the energy-transfer rate. These measurements support current models that contain dark, higher-lying excitonic states to bridge the energy gap between rings, thereby maintaining similar energy-transfer dynamics. Overall, these results demonstrate that energy-transfer dynamics in the B800–850 complex are robust to the spectral and structural variations between species used to optimize energy capture and flow in purple bacteria. [less ▲] Detailed reference viewed: 37 (2 UL)Work Statistics, Loschmidt Echo and Information Scrambling in Chaotic Quantum Systems Chenu, Aurélia ; ; Del Campo Echevarria, Adolfo in Quantum (2019), 3 Characterizing the work statistics of driven complex quantum systems is generally challenging because of the exponential growth with the system size of the number of transitions involved between different ... [more ▼] Characterizing the work statistics of driven complex quantum systems is generally challenging because of the exponential growth with the system size of the number of transitions involved between different energy levels. We consider the quantum work distribution associated with the driving of chaotic quantum systems described by random matrix Hamiltonians and characterize exactly the work statistics associated with a sudden quench for arbitrary temperature and system size. Knowledge of the work statistics yields the Loschmidt echo dynamics of an entangled state between two copies of the system of interest, the thermofield double state. This echo dynamics is dictated by the spectral form factor. We discuss its relation to frame potentials and its use to assess information scrambling. [less ▲] Detailed reference viewed: 35 (0 UL)Composite boson signature in the interference pattern of atomic dimer condensates ; Chenu, Aurélia ; in New Journal of Physics (2019), 21 We predict the existence of high frequency modes in the interference pattern of two condensates made of fermionic-atom dimers. These modes, which result from fermion exchanges between condensates ... [more ▼] We predict the existence of high frequency modes in the interference pattern of two condensates made of fermionic-atom dimers. These modes, which result from fermion exchanges between condensates, constitute a striking signature of the dimer composite nature. From the 2-coboson spatial correlation function, that we derive analytically, and the Shiva diagrams that visualize many-body effects specific to composite bosons, we identify the physical origin of these high frequency modes and determine the conditions to see them experimentally by using bound fermionic-atom pairs trapped on optical lattice sites. The dimer granularity which appears in these modes comes from Pauli blocking that prevents two dimers to be located at the same lattice site. [less ▲] Detailed reference viewed: 23 (0 UL)Two-level system coupled to phonons: Full analytical solution Chenu, Aurélia ; ; in Physical Review. B (2019), 99 We propose an analytical procedure to fully solve a two-level system coupled to phonons. Instead of using the common formulation in terms of linear and quadratic system-phonon couplings, we introduce ... [more ▼] We propose an analytical procedure to fully solve a two-level system coupled to phonons. Instead of using the common formulation in terms of linear and quadratic system-phonon couplings, we introduce different phonons depending on the system electronic level. We use this approach to recover known results for the linear-coupling limit in a simple way. More importantly, we derive results for the quadratic coupling induced by a phonon frequency change, a problem considered up to now as not analytically solvable. [less ▲] Detailed reference viewed: 35 (0 UL)Extreme Decoherence and Quantum Chaos ; ; Chenu, Aurélia et al in Physical Review Letters (2019), 122 We study the ultimate limits to the decoherence rate associated with dephasing processes. Fluctuating chaotic quantum systems are shown to exhibit extreme decoherence, with a rate that scales ... [more ▼] We study the ultimate limits to the decoherence rate associated with dephasing processes. Fluctuating chaotic quantum systems are shown to exhibit extreme decoherence, with a rate that scales exponentially with the particle number, thus exceeding the polynomial dependence of systems with fluctuating k-body interactions. Our findings suggest the use of quantum chaotic systems as a natural test bed for spontaneous wave function collapse models. We further discuss the implications on the decoherence of AdS/CFT black holes resulting from the unitarity loss associated with energy dephasing. [less ▲] Detailed reference viewed: 32 (1 UL)Shortcuts to adiabaticity in Fermi gases ; ; et al in New Journal of Physics (2018) Detailed reference viewed: 27 (0 UL)Quantum work statistics, Loschmidt echo and information scrambling Chenu, Aurélia ; ; et al in Scientific Reports (2018) Detailed reference viewed: 29 (1 UL)Superadiabatic quantum friction suppression in finite-time thermodynamics ; Chenu, Aurélia ; et al in Science Advances (2018) Detailed reference viewed: 33 (0 UL)Impact of the lipid bilayer on energy transfer kinetics in the photosynthetic protein LH2 ; ; et al in Chemical Science (2018) Detailed reference viewed: 24 (0 UL)Thermal Light as a Mixture of Sets of Pulses: the Quasi-1D Example ; Chenu, Aurélia ; in Journal of the Optical Society of America. B, Optical Physics (2017) Detailed reference viewed: 23 (0 UL) |
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