Quantum Interference in Time PhysicsWeb, Slashdot Paulus and colleagues have conducted a novel version of the double slit experiment, observing interference fringes with electrons passing through a double slit in time. Separated by femtosecond laser pulses, the 'slit' is composed of two maxima and one minima of the electric field. Slashdot notes several related articles on Zeilinger's interference experiments with fullerenes and biomolecules; see also the "delayed-choice quantum eraser" experiment by Shih and Kim.
Schwab comments on Phys. Rev. Lett. 94, 030402 (2005) arXiv In reply to the recent Gaidarzhy et al. report on "Evidence for Quantized Displacement in Macroscopic Nanomechanical Oscillators," Schwab et al. contend that the Letter contains order-of-magnitude omissions and inaccuracies counter to any interpretation of quantized macroscopic displacement: " ... the evidence, analysis, claims, and conclusions presented are contrary to expectations from fundamentals of quantum mechanics and elasticity theory, and [...] the method used by the authors is unsuitable in principle to observe the quantized energy states of a nanomechanical structure."
25 February 2005
Simultaneous State Measurement of Coupled Josephson Phase Qubits NIST, UCSB In Science [25 Feb 2005], McDermott et al. report on simultaneous precision measurement of antiphase oscillation between flux qubits, consistent with entanglement of the two qubit states. "One of the many challenges of building a scalable quantum computer is single-shot measurement of all the quantum bits. Here, we exploit the simultaneous single-shot measurement of two coupled Josephson phase qubits to directly probe interaction of the qubits in the time domain [...] thereby opening the possibility for the full characterization of multi-qubit gates and elementary quantum algorithms."
18 February 2005
Quantum Leap canada.com A brief overview of the history and development of quantum cryptography, from its origins through a chance encounter between Charles Bennett and Giles Brassard while swimming in the warm tropical waters of the Caribbean, to the next-generation satellite-based quantum encryption links of tomorrow. "Together, Brassard and Bennett would go on to found a field of science - quantum information processing - whose effects on society some say could even rival the impact that the steam engine had in its time."
10 February 2005
Schrodinger's Kittens Mohanty Group In Physical Review Letters [ 28 Jan 2005 ], the Mohanty Group at Boston University reports evidence of [center-of-mass displacement] quantum nanomechanical oscillations in silicon antennae of ~ 50 billion atoms, making this the largest observation of quantum mechanical behavior to date. "It's a truly macroscopic quantum system," says Alexei Gaidarzhy, the paper's lead author and a graduate student in the BU College of Engineering's Department of Aerospace and Mechanical Engineering. "When it's a new phenomenon, it's best not to be guided by expectations based on conventional wisdom. The philosophy here is to let the data speak for itself."
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