437 research outputs found
Observation of Strong Coulomb Blockade in Resistively Isolated Tunnel Junctions
We report measurements of the Coulomb-blockade current in resistively
isolated (R_{Isol} >> h/e^{2}) tunnel junctions for the temperature range 60mK
R_{Isol}\gg h/e^{2})$ tunnel junctions for the temperature range 60mK < T <
230mK where the charging energy E_{c} is much greater than the thermal energy.
A zero-bias resistance R_{0} of up to 10^{4}R_{T} (the tunnel resistance of the
bare junction) is obtained. For eV << E_{c}, the I-V curves for a given
R_{Isol} scale as a function of V/T, with I \propto V^{\alpha (R_{Isol})} over
a range of V. The data agree well with numerical calculations of the tunneling
rate that include environmental effects.Comment: 13 pages, 3 eps figure
Entangling two oscillators with arbitrary asymmetric initial states
A Hamiltonian is presented, which can be used to convert any asymmetric state
of two oscillators and into an
entangled state. Furthermore, with this Hamiltonian and local operations only,
two oscillators, initially in any asymmetric initial states, can be entangled
with a third oscillator. The prepared entangled states can be engineered with
an arbitrary degree of entanglement. A discussion on the realization of this
Hamiltonian is given. Numerical simulations show that, with current circuit QED
technology, it is feasible to generate high-fidelity entangled states of two
microwave optical fields, such as entangled coherent states, entangled squeezed
states, entangled coherent-squeezed states, and entangled cat states. Our
finding opens a new avenue for creating not only two-color or three-color
entanglement of light but also wave-like or particle-like entanglement or novel
wave-like and particle-like hybrid entanglement.Comment: 8 pages, 2 figure
Orbital angular momentum mode-demultiplexing scheme with partial angular receiving aperture
For long distance orbital angular momentum (OAM) based transmission, the conventional whole beam receiving scheme encounters the difficulty of large aperture due to the divergence of OAM beams. We propose a novel partial receiving scheme, using a restricted angular aperture to receive and demultiplex multi-OAM-mode beams. The scheme is theoretically analyzed to show that a regularly spaced OAM mode set remain orthogonal and therefore can be de-multiplexed. Experiments have been carried out to verify the feasibility. This partial receiving scheme can serve as an effective method with both space and cost savings for the OAM communications. It is applicable to both free space OAM optical communications and radio frequency (RF) OAM communications
Generating entanglement between microwave photons and qubits in multiple cavities coupled by a superconducting qutrit
We discuss how to generate entangled coherent states of four
\textrm{microwave} resonators \textrm{(a.k.a. cavities)} coupled by a
superconducting qubit. We also show \textrm{that} a GHZ state of four
superconducting qubits embedded in four different resonators \textrm{can be
created with this scheme}. In principle, \textrm{the proposed method} can be
extended to create an entangled coherent state of resonators and to prepare
a Greenberger-Horne-Zeilinger (GHZ) state of qubits distributed over
cavities in a quantum network. In addition, it is noted that four resonators
coupled by a coupler qubit may be used as a basic circuit block to build a
two-dimensional quantum network, which is useful for scalable quantum
information processing.Comment: 13 pages, 7 figure
Generation of GHZ entangled states of photons in multiple cavities via a superconducting qutrit or an atom through resonant interaction
We propose an efficient method to generate a GHZ entangled state of n photons
in n microwave cavities (or resonators) via resonant interaction to a single
superconducting qutrit. The deployment of a qutrit, instead of a qubit, as the
coupler enables us to use resonant interactions exclusively for all
qutrit-cavity and qutrit-pulse operations. This unique approach significantly
shortens the time of operation which is advantageous to reducing the adverse
effects of qutrit decoherence and cavity decay on fidelity of the protocol.
Furthermore, the protocol involves no measurement on either the state of qutrit
or cavity photons. We also show that the protocol can be generalized to other
systems by replacing the superconducting qutrit coupler with different types of
physical qutrit, such as an atom in the case of cavity QED, to accomplish the
same task.Comment: 11 pages, 5 figures, accepted by Phys. Rev.
- …