15 research outputs found
Universal teleportation with a twist
We give a transfer theorem for teleportation based on twisting the
entanglement measurement. This allows one to say what local unitary operation
must be performed to complete the teleportation in any situation, generalizing
the scheme to include overcomplete measurements, non-abelian groups of local
unitary operations (e.g., angular momentum teleportation), and the effect of
non-maximally entangled resources.Comment: 4 pages, 1 figur
Quantum cryptography with squeezed states
A quantum key distribution scheme based on the use of displaced squeezed
vacuum states is presented. The states are squeezed in one of two field
quadrature components, and the value of the squeezed component is used to
encode a character from an alphabet. The uncertainty relation between
quadrature components prevents an eavesdropper from determining both with
enough precision to determine the character being sent. Losses degrade the
performance of this scheme, but it is possible to use phase-sensitive
amplifiers to boost the signal and partially compensate for their effect.Comment: 15 pages, no figure
Soliton Squeezing in a Mach-Zehnder Fiber Interferometer
A new scheme for generating amplitude squeezed light by means of soliton
self-phase modulation is experimentally demonstrated. By injecting 180-fs
pulses into an equivalent Mach-Zehnder fiber interferometer, a maximum noise
reduction of dB is obtained ( dB when corrected for
losses). The dependence of noise reduction on the interferometer splitting
ratio and fiber length is studied in detail.Comment: 5 pages, 4 figure
Canonical Quantum Teleportation
Canonically conjugated observables such as position-momentum and phase-number
are found to play a 3-fold role in the drama of the quantum teleportation.
Firstly, the common eigenstate of two commuting canonical observables like
phase-difference and number-sum provides the quantum channel between two
systems. Secondly, a similar pair of canonical observables from another two
systems is measured in the Bell operator measurements.Comment: revtex,4 pages,e-mail:[email protected] www.itp.ac.cn/~suncp; The
Institute of Theoretical Physics, Academia Sinica, Beijing 100080, P.R. Chin
Quantitative wave-particle duality and non-erasing quantum erasure
The notion of wave-particle duality may be quantified by the inequality
V^2+K^2 <=1, relating interference fringe visibility V and path knowledge K.
With a single-photon interferometer in which polarization is used to label the
paths, we have investigated the relation for various situations, including
pure, mixed, and partially-mixed input states. A quantum eraser scheme has been
realized that recovers interference fringes even when no which-way information
is available to erase.Comment: 6 pages, 4 figures. To appear in Phys. Rev.
Decoherence in trapped ions due to polarization of the residual background gas
We investigate the mechanism of damping and heating of trapped ions
associated with the polarization of the residual background gas induced by the
oscillating ions themselves. Reasoning by analogy with the physics of surface
electrons in liquid helium, we demonstrate that the decay of Rabi oscillations
observed in experiments on 9Be+ can be attributed to the polarization phenomena
investigated here. The measured sensitivity of the damping of Rabi oscillations
with respect to the vibrational quantum number of a trapped ion is also
predicted in our polarization model.Comment: 26 pdf pages with 5 figures, http://www.df.ufscar.br/~quantum
High Frequency Acousto-electric Single Photon Source
We propose a single optical photon source for quantum cryptography based on the acousto-electric effect. Surface acoustic waves (SAWs) propagating through a quasi-one-dimensional channel have been shown to produce packets of electrons which reside in the SAW minima and travel at the velocity of sound. In our scheme these electron packets are injected into a p-type region, resulting in photon emission. Since the number of electrons in each packet can be controlled down to a single electron, a stream of single (or N) photon states, with a creation time strongly correlated with the driving acoustic field, should be generated