01 September 2010


Are we living in a designer universe
 
MIT, Sussex "Creating a new universe would require a machine only slightly more powerful than the LHC—and there is every chance that our own universe may have been manufactured in this way.
  – John Gribbin, Telegraph
"A basement universe possesses a fate independent of its parent: harnessing the zero-point energy to trigger inflation becomes a form of applied cosmological engineering. And if basement universes are a naturally occurring phenomenon, as suggested by inflationary cosmological models, the multiverse then takes on the characteristics of an evolutionary algorithm. Though the parent universe in any branching scenario need not have been of intelligent design, once a suitable set of cosmological constants is found through natural inflation, intelligent life could branch out from this point of origin, forming an expanding wavefront of intelligence and altering the evolution of the multiverse itself [...] 
Given that the conditions of the Drake equation are met, a potential explanation for the silence in our immediate neighborhood of the cosmos is that inter-universe panspermia supercedes local expansion. Vernor Vinge’s Singularity may not be only technological; it may be physical. The most powerful computer we can imagine would for all intensive purposes resemble a black hole."
   – C. Altman, Expansion Scenarios 

27 August 2010

Is reality even stranger than quantum mechanics tells us? 
"We know that quantum correlations can be stronger than classical—but why aren't quantum correlations even stronger? Either we are missing something very significant to define quantum theory, or these other theories are all around us too."
 – Caslav Brukner (New Scientist)

12 August 2010

Any quantum state can be cloned in the presence of closed timelike curves  "The possible existence of closed timelike curves (CTCs) draws attention to fundamental questions about what is physically possible and what is not. An example is the "no cloning theorem" in quantum mechanics — which states that no physical means exists by which an unknown arbitrary quantum state can be reproduced, or copied perfectly. We show here that this theorem can be circumvented in the presence of closed timelike curves, allowing for the cloning of an unknown arbitrary quantum state. Since the "no cloning theorem" has played a central role in the development of quantum information science, it is clear that the existence of CTCs would radically change the rules for quantum information technology.
– Tim Ralph, David Ahn, R. B. Mann (arXiv:1008.0221)

06 August 2010

Molecular Simulation with Superconducting Qubits 
"Because Nature isn't classical, damnit, and if you want to make a simulation of nature, you'd better make it quantum mechanical. " —Richard Feynman 
Georgia, UCSB In arXiv:1008.0701, Pritchett, Martinis et al. introduce a protocol for efficient simulation of molecular dynamics using superconducting qubits. "Recent experimental progress suggests that quantum simulation will be one of the first practical applications of quantum computation. We have shown how quantum computers of only a few qubits can simulate arbitrary quantum systems accurately and quickly, even before they reach the regime of fault tolerant quantum computation."

17 July 2010

Decoherence sources in coupled flux qubits NEC, RIKEN In Phys Rev B and concurrent arXiv preprints, Yoshihara, Nakamura and Tsai study decoherence in coupled superconducting flux qubits. "The microscopic origin of decoherence has been elusive so far. It is crucial to identify and eliminate the source of noise sources in order to improve the performance of these devices—the sensitivity of SQUIDs and coherence of qubits. We have quantified the correlations among flux noise and found that the dominant contribution is by local fluctuations."

18 June 2010

Superconducting qubits as artificial atoms
"The demonstrated resonance wave scattering indicates that superconducting quantum devices can be used as building blocks for controllable, quantum coherent, macroscopic artificial structures — in which a plethora of effects can be realized from quantum optics of atomic systems."
NEC 東京大学 This week's Qulink seminar by Yasunobu Nakamura (NEC) reports on recent developments in exploring the quantum optical properties of a superconducting flux qubit coupled to a 1d microwave transmission line. See also: Electromagnetically induced transparency on a single artificial atom (arXiv); Resonance fluorescence of a single artificial atom (Science); Ultimate on-chip quantum amplifier (Phys Rev Lett).

11 June 2010

Quantum Zeno effect with a superconducting qubit NTT In arXiv 1006.2133, Matsuzaki and Semba provide detailed analysis of the Quantum Zeno effect in superconducting qubits: "Superconducting qubits are a promising system to observe the Quantum Zeno effect. We have studied how a sequence of projective measurements can alter the dephasing process, and suggest experimental requirements to observe the Quantum Zeno effect in existing superconducting qubits. It would be possible to demonstrate our prediction utilizing current technologies."