4,912 research outputs found
Quantum state transmission in a cavity array via two-photon exchange
The dynamical behavior of a coupled cavity array is investigated when each
cavity contains a three-level atom. For the uniform and staggered intercavity
hopping, the whole system Hamiltonian can be analytically diagonalized in the
subspace of single-atom excitation. The quantum state transfer along the
cavities is analyzed in detail for distinct regimes of parameters, and some
interesting phenomena including binary transmission, selective localization of
the excitation population are revealed. We demonstrate that the uniform
coupling is more suitable for the quantum state transfer. It is shown that the
initial state of polariton located in the first cavity is crucial to the
transmission fidelity, and the local entanglement depresses the state transfer
probability. Exploiting the metastable state, the distance of the quantum state
transfer can be much longer than that of Jaynes-Cummings-Hubbard model. A
higher transmission probability and longer distance can be achieved by
employing a class of initial encodings and final decodings.Comment: 8 pages, 7 figures. to appear in Phys. Rev.
Improved ACD-based financial trade durations prediction leveraging LSTM networks and Attention Mechanism
The liquidity risk factor of security market plays an important role in the
formulation of trading strategies. A more liquid stock market means that the
securities can be bought or sold more easily. As a sound indicator of market
liquidity, the transaction duration is the focus of this study. We concentrate
on estimating the probability density function p({\Delta}t_(i+1) |G_i) where
{\Delta}t_(i+1) represents the duration of the (i+1)-th transaction, G_i
represents the historical information at the time when the (i+1)-th transaction
occurs. In this paper, we propose a new ultra-high-frequency (UHF) duration
modelling framework by utilizing long short-term memory (LSTM) networks to
extend the conditional mean equation of classic autoregressive conditional
duration (ACD) model while retaining the probabilistic inference ability. And
then the attention mechanism is leveraged to unveil the internal mechanism of
the constructed model. In order to minimize the impact of manual parameter
tuning, we adopt fixed hyperparameters during the training process. The
experiments applied to a large-scale dataset prove the superiority of the
proposed hybrid models. In the input sequence, the temporal positions which are
more important for predicting the next duration can be efficiently highlighted
via the added attention mechanism layer
Fidelity, dynamic structure factor, and susceptibility in critical phenomena
Motivated by the growing importance of fidelity in quantum critical
phenomena, we establish a general relation between fidelity and structure
factor of the driving term in a Hamiltonian through a newly introduced concept:
fidelity susceptibility. Our discovery, as shown by some examples, facilitates
the evaluation of fidelity in terms of susceptibility using well developed
techniques such as density matrix renormalization group for the ground state,
or Monte Carlo simulations for the states in thermal equilibrium.Comment: 4 pages, 2 figures, final version accepted by PR
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