arXiv subjects

Ping Koy Lam

Publications and source records attributed to Ping Koy Lam.

152 records · Page 9Linked to original sources

arXiv2004

Tripartite Quantum State Sharing

We demonstrate a multipartite protocol to securely distribute and reconstruct a quantum state. A secret quantum state is encoded into a tripartite entangled state and distributed to three players. Any two of the three players are able to reconstruct the state, whilst individual players obtain nothing. We characterize this (2,3) threshold quantum state sharing scheme in terms of fidelity, signal transfer and reconstruction noise. We demonstrate a fidelity averaged over all reconstruction permutations of 0.73, which is achievable only using quantum resources.

quant-ph↗

arXiv2003

Study of an electro-optic modulator capable of generating simultaneous amplitude and phase modulations

We report on the analysis and prototype-characterization of a dual-electrode electro-optic modulator that can generate both amplitude and phase modulations with a selectable relative phase, termed a universally tunable modulator (UTM). All modulation states can be reached by tuning only the electrical inputs, facilitating real-time tuning, and the device is shown to have good suppression and stability properties. A mathematical analysis is presented, including the development of a geometric phase representation for modulation. The experimental characterization of the device shows that relative suppressions of 38 dB, 39 dB and 30 dB for phase, single-sideband and carrier-suppressed modulations, respectively, can be obtained, as well as showing the device is well-behaved when scanning continuously through the parameter space of modulations. Uses for the device are discussed, including the tuning of lock points in optical locking schemes, single sideband applications, modulation fast-switching applications, and applications requiring combined modulations.

gr-qc↗

arXiv2003

Continuous variable polarization entanglement, experiment and analysis

We generate and characterise continuous variable polarization entanglement between two optical beams. We first produce quadrature entanglement, and by performing local operations we transform it into a polarization basis. We extend two entanglement criteria, the inseparability criteria proposed by Duan {\it et al.}\cite{Duan00} and the Einstein-Podolsky-Rosen paradox criteria proposed by Reid and Drummond\cite{Reid88}, to Stokes operators; and use them to charactise the entanglement. Our results for the Einstein-Podolsky-Rosen paradox criteria are visualised in terms of uncertainty balls on the Poincaré sphere. We demonstrate theoretically that using two quadrature entangled pairs it is possible to entangle three orthogonal Stokes operators between a pair of beams, although with a bound $\sqrt{3}$ times more stringent than for the quadrature entanglement.

quant-ph↗

arXiv2002

Experimental demonstration of continuous variable polarization entanglement

We report the experimental transformation of quadrature entanglement between two optical beams into continuous variable polarization entanglement. We extend the inseparability criterion proposed by Duan, et al. [Duan00] to polarization states and use it to quantify the entanglement between the three Stokes operators of the beams. We propose an extension to this scheme utilizing two quadrature entangled pairs for which all three Stokes operators between a pair of beams are entangled.

quant-ph↗

arXiv2002

Stokes operator squeezed continuous variable polarization states

We investigate quantum correlations in continuous wave polarization squeezed laser light generated from one and two optical parametric amplifiers, respectively. A general expression of how Stokes operator variances decompose into two mode quadrature operator variances is given. Stokes parameter variance spectra for four different polarization squeezed states have been measured and compared with a coherent state. Our measurement results are visualized by three-dimensional Stokes operator noise volumes mapped on the quantum Poincare sphere. We quantitatively compare the channel capacity of the different continuous variable polarization states for communication protocols. It is shown that squeezed polarization states provide 33% higher channel capacities than the optimum coherent beam protocol.

quant-ph↗

arXiv2002

Experimental investigation of continuous variable quantum teleportation

We report the experimental demonstration of quantum teleportation of the quadrature amplitudes of a light field. Our experiment was stably locked for long periods, and was analyzed in terms of fidelity, F; and with signal transfer, T_{q}=T^{+}+T^{-}, and noise correlation, V_{q}=V_{in|out}^{+} V_{in|out}^{-}. We observed an optimum fidelity of 0.64 +/- 0.02, T_{q}= 1.06 +/- 0.02 and V_{q} =0.96 +/- 0.10. We discuss the significance of both T_{q}>1 and V_{q}<1 and their relation to the teleportation no-cloning limit.

quant-ph↗

arXiv2002

Experimental demonstration of a squeezing enhanced power recycled Michelson interferometer for gravitational wave detection

Interferometric gravitational wave detectors are expected to be limited by shot noise at some frequencies. We experimentally demonstrate that a power recycled Michelson with squeezed light injected into the dark port can overcome this limit. An improvement in the signal-to-noise ratio of 2.3dB is measured and locked stably for long periods of time. The configuration, control and signal readout of our experiment are compatible with current gravitational wave detector designs. We consider the application of our system to long baseline interferometer designs such as LIGO.

quant-ph↗

arXiv2001

Polarization Squeezing of Continuous Variable Stokes Parameters

We report the first direct experimental characterization of continuous variable quantum Stokes parameters. We generate a continuous wave light beam with more than 3 dB of simultaneous squeezing in three of the four Stokes parameters. The polarization squeezed beam is produced by mixing two quadrature squeezed beams on a polarizing beam splitter. Depending on the squeezed quadrature of these two beams the quantum uncertainty volume on the Poincaré sphere became a `cigar' or `pancake'-like ellipsoid.

quant-ph↗