D. J. Szwer

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We create entangled states of the spin and motion of a single 40Ca+ ion in a linear ion trap. We theoretically study and experimentally observe the behavior outside the Lamb-Dicke regime, where the trajectory in phase space is modified and the motional coherent states become squeezed. We directly observe the modification of the return time of the(More)
We use a microwave field to control the quantum state of optical photons stored in a cold atomic cloud. The photons are stored in highly excited collective states (Rydberg polaritons) enabling both fast qubit rotations and control of photon-photon interactions. Through the collective read-out of these pseudospin rotations it is shown that the microwave(More)
Entanglement is one of the most fundamental properties of quantum mechanics, and is the key resource for quantum information processing (QIP). Bipartite entangled states of identical particles have been generated and studied in several experiments, and post-selected or heralded entangled states involving pairs of photons, single photons and single atoms, or(More)
We describe and implement a method to restore the state of a single qubit, in principle perfectly, after it has partially collapsed. The method resembles the classical Hahn spin echo but works on a wider class of relaxation processes, in which the quantum state partially leaves the computational Hilbert space. It is not guaranteed to work every time, but(More)
In this work we propose a hybrid scheme using electromagnetically induced transparency (EIT) and the dipole blockade between Rydberg atoms and their interactions with microwave fields. This scheme makes use of the spatial properties of the blockade phenomenon to realize a controlled-z, photonic phase gate which works with all fields on resonance, where the(More)
We demonstrate single-shot qubit readout with fidelity sufficient for fault-tolerant quantum computation , for two types of qubit stored in single trapped calcium ions. For an optical qubit stored in the (4S1/2, 3D5/2) levels of 40 Ca + we achieve 99.991(1)% average readout fidelity in one million trials, using time-resolved photon counting. An adaptive(More)
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