670 research outputs found
Generation of Dicke States with Phonon-Mediated Multi-level Stimulated Raman Adiabatic Passage
We generate half-excited symmetric Dicke states of two and four ions. We use
multi-level stimulated Raman adiabatic passage (STIRAP) whose intermediate
states are phonon Fock states. This process corresponds to the spin squeezing
operation and half-excited Dicke states are generated during multi-level
STIRAP. This method does not require local access for each ion or the
preparation of phonon Fock states. Furthermore, it is robust since it is an
adiabatic process. We evaluate the Dicke state using a witness operator and
determine the upper and lower bounds of the fidelity without using full quantum
tomography.Comment: 5pages, 4 figure
Quantum State Engineering using Single Nuclear Spin Qubit of Optically Manipulated Ytterbium Atom
A single Yb atom is loaded into a high-finesse optical cavity with a moving
lattice, and its nuclear spin state is manipulated using a nuclear magnetic
resonance technique. A highly reliable quantum state control with fidelity and
purity greater than 0.98 and 0.96, respectively, is confirmed by the full
quantum state tomography; a projective measurement with high speed (500us) and
high efficiency (0.98) is accomplished using the cavity QED technique. Because
a hyperfine coupling is induced only when the projective measurement is
operational, the long coherence times (T_1 = 0.49 s and T_2 = 0.10 s) are
maintained. Our technique can be applied for implementing a scalable one-way
quantum computation with a cluster state in an optical lattice.Comment: 4 figure
Generation of a decoherence-free entangled state using a radio frequency dressed state
We propose the generation of entangled states with trapped calcium ions using
a combination of an rf dressed state and a spin dependent force. Using this
method, a decoherence-free entangled state of rf qubits can be directly
generated and ideally its fidelity is close to unity. We demonstrate an rf
entangled state with a fidelity of 0.68, which has a coherence time of more
than 200 ms by virtue of the fact that it is an eigenstate with energy gaps
between adjacent levels.Using the same technique, we also produce a
qutrit-qutrit entangled state with a fidelity of 0.77, which exceeds the
threshold value for separability of 2/3.Comment: 4 figure
Quantum magnonics: magnon meets superconducting qubit
The techniques of microwave quantum optics are applied to collective spin
excitations in a macroscopic sphere of ferromagnetic insulator. We demonstrate,
in the single-magnon limit, strong coupling between a magnetostatic mode in the
sphere and a microwave cavity mode. Moreover, we introduce a superconducting
qubit in the cavity and couple the qubit with the magnon excitation via the
virtual photon excitation. We observe the magnon-vacuum-induced Rabi splitting.
The hybrid quantum system enables generation and characterization of
non-classical quantum states of magnons.Comment: 10 pages, 6 figure
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