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Quantum speed limits on operator flows and correlation functions Carabba, Nicoletta ; Hörnedal, Niklas ; Del Campo Echevarria, Adolfo in Quantum (2022), 6 Detailed reference viewed: 37 (0 UL)Analyticity constraints bound the decay of the spectral form factor Chenu, Aurélia ; Martinez Azcona, Pablo in Quantum (2022) Detailed reference viewed: 23 (0 UL)Quantum scattering as a work source ; Esposito, Massimiliano ; et al in Quantum (2022), 6 Detailed reference viewed: 17 (0 UL)QKD parameter estimation by two-universal hashing leads to faster convergence to the asymptotic rate Ostrev, Dimiter in Quantum (2021) This paper proposes and proves security of a QKD protocol which uses two-universal hashing instead of random sampling to estimate the number of bit flip and phase flip errors. This protocol dramatically ... [more ▼] This paper proposes and proves security of a QKD protocol which uses two-universal hashing instead of random sampling to estimate the number of bit flip and phase flip errors. This protocol dramatically outperforms previous QKD protocols for small block sizes. More generally, for the two-universal hashing QKD protocol, the difference between asymptotic and finite key rate decreases with the number $n$ of qubits as $cn^{-1}$, where $c$ depends on the security parameter. For comparison, the same difference decreases no faster than $c'n^{-1/3}$ for an optimized protocol that uses random sampling and has the same asymptotic rate, where $c'$ depends on the security parameter and the error rate. [less ▲] Detailed reference viewed: 63 (9 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: 66 (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: 33 (1 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: 32 (0 UL) |
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