Quantum state reconstruction on atom-chips

Abstract

We realize on an atom-chip, a practical, experimentally undemanding, tomographic reconstruction algorithm relying on the time-resolved measurements of the atomic population distribution among atomic internal states. More specifically, we estimate both the state density matrix, as well as the dephasing noise present in our system, by assuming complete knowledge of the Hamiltonian evolution. The proposed scheme is based on routinely performed measurements and established experimental procedures, hence providing a simplified methodology for quantum technological applications.

One decade of quantum optimal control in the chopped random basis

“…To this end, the control pulses were designed by open-loop CRAB optimization of the frequency-modulated radio-frequency (rf) pulses using 7 random frequency basis functions and the state preparation was numerically predicted at ≈ 3% error in the final population distribution. The tomographic reconstruction developed in [183] confirmed that the density matrix of the prepared state was in agreement with the theoretical prediction with a fidelity higher than 0.9, and demonstrated that the optimized rf pulses outperformed the unoptimized pulses even for shorter pulse duration, paving the way to overcoming the unavoidable and detrimental dephasing of the levels.…”

“…On a similar setup of a BEC on an atom chip, a protocol for the tomographic reconstruction of a quantum state was demonstrated based on time-resolved measurements of the atomic population distribution among the internal BEC states, implemented by an optimization protocol that minimized the difference between the measured data and the numerical simulation [183]. This provides a simple yet highly advantageous tomographic method, which makes use of a post-processing optimization procedure and a standard absorption imaging technique.…”

Experimental Realization of Optimal Time‐Reversal on an Atom Chip for Quantum Undo Operations

“…In this regard, by making use of the results in refs. [33, 48] concerning the optimal preparation of quantum states on 87 Rb BEC atom‐chip‐based micro‐traps, we implement a preliminary test experiment to tune the values of the setup parameters (i.e., the constant magnetic field and Rabi frequency) for accurate state preparation and transfer. In this test experiment, we compare the theoretical and experimentally measured time evolutions of the atomic population in each of the five $$m_F$$ sub‐levels during the application of an optimal pulse.…”

Experimental realization of optimal time-reversal on an atom chip for quantum undo operations

“…In this regard, by making use of the results in Refs. [32,47] concerning the optimal preparation of quantum states on 87 Rb BEC atom-chip-based micro-traps, we implement a preliminary test experiment to tune the values of the setup parameters (i.e., the constant magnetic field and Rabi frequency) for accurate state preparation and transfer. In this test experiment, we compare the theoretical and experimentally measured time evolutions of the atomic population in each of the five m F sub-levels during the application of an optimal pulse.…”