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Payman Mahmoudi

Publications and source records attributed to Payman Mahmoudi.

4 recordsLinked to original sources

Disorder-blind Mpemba acceleration of quantum state preparation

Using the strong Mpemba effect to accelerate relaxation by initial-state design requires suppressing the slowest mode, which typically needs prior knowledge of the system. However, in disordered systems, this mode is sample-dependent, so a fixed preparation generally retains a slow-mode overlap. We show that a ``blind'' preparation, designed from the clean chain without knowledge of the disorder realisation or its distribution, can start farther from stationarity yet overtake a reference in typical samples of a dephased disordered XX chain. It requires only the chain geometry and the particle number. At strong dephasing, the density dynamics maps to a resistor chain, and an exact inverse-generator identity links the residual overlap to the spatial resistance profile. We find two distinct thresholds: a finite mean resistance suffices for diffusion, but the residual overlap decays as $L^{-1/2}$ with chain length $L$ only when the resistance variance is finite; rare weak links slow this decay. We predict the fraction of samples in which the blind preparation wins, which is an ensemble-level measure of its reliability. Finite-size calculations support both scaling regimes with interactions at strong dephasing. We give preparation circuits and a density readout for the residual overlap.

quant-ph↗

Theoretical Study of Classical Dynamics of Electron in Two-Frequency Paul Trap

We present a theoretical study of trapping an electron in a two-frequency Paul trap, motivated by future hybrid architecture consisting of a doubly charged calcium ion (Ca$^{2+}$) and an electron. By isolating the electron from ionic-electron interactions, we formulate the equations of motion for the electron in the time-dependent trap potentials and cast them in the Hill form. Stability and dynamics are then analysed in terms of the dimensionless q-parameters, which encode the applied voltages, drive frequencies, trap geometry, and the particle's charge-to-mass ratio. Under the combined action of the two radio-frequency fields, the trapped electron's classical motion is shown to be approximated well by a slow secular oscillation modulated by two distinct motion sidebands originating from the low- and high-frequency RF drives. The approximation method presented here enables a quick evaluation of the relation between the device-design q-parameters and the electron motion. It offers a crucial foundation for developing physical models of electron-ion interactions in electron-ion traps.

physics.atom-ph↗

Optimal quantum sensing of the nonlinear bosonic interactions using Fock states

Nonlinear processes with individual quanta beyond bilinear interactions are essential for quantum technology with bosonic systems. Diverse coherent splitting and merging of quanta in them already manifest in the estimation of their nonlinear coupling from observed statistics. We derive non-trivial, but optimal strategies for sensing the basic and experimentally available trilinear interactions using non-classical particle-like Fock states as a probe and feasible measurement strategies. Remarkably, the optimal probing of nonlinear coupling reaches estimation errors scaled down with $N^{-1/3}$ for overall $N$ of quanta in specific but available high-quality Fock states in all interacting modes. It can reveal unexplored aspects of nonlinear dynamics relevant to using such nonlinear processes in bosonic experiments with trapped ions and superconducting circuits and opens further developments of quantum technology with them.

quant-ph↗

The effect of noisy environment on Secure Quantum Teleportation of uni-modal Gaussian states

Quantum communication networks can be built on quantum teleportation, which is the transmission of an unknown quantum state from a sending station to a remote receiving station supported by entangled states and classical communication. We use a continuous variable two-mode squeezed vacuum state as a resource state for the quantum teleportation. This state is shared by Alice and Bob, and their system comes into contact with a squeezed thermal environment. The conditions for a secure quantum teleportation require a teleportation fidelity larger than 2/3 and two-way steering of the resource state. We investigate the time evolution of the steering and the fidelity of teleportation in order to determine the values of the parameters required for a successful secure quantum teleportation of a coherent Gaussian state. We show that the temperature, dissipation rate and squeezing parameter of the squeezed thermal reservoir limit the feasible duration for secure quantum teleportation, while by increasing the squeezing parameter of the initial state one can effectively expand the temporal range for a successful secure quantum teleportation.

quant-ph↗