In this letter we present a strategy that combines the action of cavity damping mechanisms with that of an engineered atomic reservoir to drive an initial thermal distribution to a Fock equilibrium state. The same technique can be used to slice probability distributions in the Fock space, thus allowing the preparation of a variety of nonclassical equilibrium states.
We describe the preparation of atom-number states with strongly interacting bosons in one dimension, or spin-polarized fermions. The procedure is based on a combination of weakening and squeezing of the trapping potential. For the resulting state, the full atom number distribution is obtained. Starting with an unknown number of particles $N_i$, we optimize the sudden change in the trapping potential which leads to the Fock state of $N_f$ particles in the final trap. Non-zero temperature effects as well as different smooth trapping potentials are analyzed. A simple criterion is provided to ensure the robust preparation of the Fock state for physically realistic traps.
We propose a scheme for generating atomic NOON states via adiabatic passage. In the scheme, a double $Lambda$-type three-level atom is trapped in a bimodal cavity and two sets of $Lambda$-type three-level atoms are translated into and outside of two single mode cavities respectively. The three cavities connected by optical fibres are always in vacuum states. After a series of operations and suitable interaction time, we can obtain arbitrary large-$n$ NOON states of two sets of $Lambda$-type three-level atoms in distant cavities by performing a single projective measurement on the double $Lambda$-type three-level atom. Due to adiabatic elimination of atomic excited states and the application of adiabatic passage, our scheme is robust against the spontaneous emissions of atoms, the decays of fibres and cavities photon leakage. So the scheme has a high fidelity and feasibility under the current available techniques.
We use coherent excitation of 3-16 atom ensembles to demonstrate collective Rabi flopping mediated by Rydberg blockade. Using calibrated atom number measurements, we quantitatively confirm the expected $sqrt{N}$ Rabi frequency enhancement to within 4%. The resulting atom number distributions are consistent with essentially perfect blockade. We then use collective Rabi $pi$ pulses to produce ${cal N}=1,2$ atom number Fock states with fidelities of 62% and 48% respectively. The ${cal N}=2$ Fock state shows the collective Rabi frequency enhancement without corruption from atom number fluctuations.
We present a physical scheme for entanglement concentration of unknown atomic entangled states via cavity decay. In the scheme, the atomic state is used as stationary qubit and photonic state as flying qubit, and a close maximally entangled state can be obtained from pairs of partially entangled states probabilistically.
Quantum simulations are becoming an essential tool for studying complex phenomena, e.g. quantum topology, quantum information transfer, and relativistic wave equations, beyond the limitations of analytical computations and experimental observations. To date, the primary resources used in proof-of-principle experiments are collections of qubits, coherent states or multiple single-particle Fock states. Here we show the first quantum simulation performed using genuine higher-order Fock states, with two or more indistinguishable particles occupying the same bosonic mode. This was implemented by interfering pairs of Fock states with up to five photons on an interferometer, and measuring the output states with photon-number-resolving detectors. Already this resource-efficient demonstration reveals new topological matter, simulates non-linear systems and elucidates a perfect quantum transfer mechanism which can be used to transport Majorana fermions.