Andrew M. Lance

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We propose a new coherent state quantum key distribution protocol that eliminates the need to randomly switch between measurement bases. This protocol provides significantly higher secret key rates with increased bandwidths than previous schemes that only make single quadrature measurements. It also offers the further advantage of simplicity compared to all(More)
Quantum computers have the capability of out-performing their classical counterparts for certain computational problems. Several scalable quantum-computing architectures have been proposed. An attractive architecture is a large set of physically independent qubits arranged in three spatial regions where (1) the initialized qubits are stored in a register,(More)
This paper investigates the design of low-complexity error correction codes for the verification step in continuous variable quantum key distribution (CVQKD) systems. We design new coding schemes based on quasi-cyclic repeat-accumulate codes which demonstrate good performances for CVQKD reconciliation. Given quasi-cyclic repeat-accumulate codes' commercial(More)
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. By collaborating, any two of the three players can reconstruct the state, while individual players obtain nothing. We characterize this (2,3) threshold quantum(More)
We realize an end-to-end no-switching quantum key distribution protocol using continuous-wave coherent light. We encode weak broadband Gaussian modulations onto the amplitude and phase quadratures of light beams. Our no-switching protocol achieves high secret key rate via a post-selection protocol that utilizes both quadrature information simultaneously. We(More)
Andrew M. Lance,1 Thomas Symul,1 Warwick P. Bowen,1, 2 Barry C. Sanders,3 Tomáš Tyc,4 T. C. Ralph,5 and Ping Koy Lam1 Quantum Optics Group, Department of Physics, Faculty of Science, Australian National University, ACT 0200, Australia Quantum Optics Group, Norman Bridge Laboratory of Physics California Institute of Technology, Pasadena, CA 91125, U.S.A.(More)
The random switching of measurement bases is commonly assumed to be a necessary step of quantum key distribution protocols. In this paper we show that switching is not required for coherent state continuous variable quantum key distribution. We show this via the no-switching protocol which results in higher information rates and a simpler experimental(More)
The focus of this work is on the design of Raptor codes for continuous variable Quantum key distribution (CVQKD) systems. We design a highly efficient Raptor code for very low signal to noise ratios (SNRs), which enables CV-QKD systems to operate over long distances with a significantly higher secret key rate compared to conventional fixed rate codes. The(More)
We present two schemes to perform continuous variable (2, 3) threshold quantum secret sharing (QSS) on the quadrature amplitudes of bright light beams. Both schemes require a pair of entangled light beams. The first scheme utilizes two phase sensitive optical amplifiers, whilst the second uses an electro-optic feedforward loop for the reconstruction of the(More)
We present an optical system designed to capture and observe a single neutral atom in an optical dipole trap, created by focussing a laser beam using a large numerical aperture (N.A. = 0.5) aspheric lens. We experimentally evaluate the performance of the optical system and show that it is diffraction limited over a broad spectral range (∼ 200 nm) with a(More)