Wednesday, March 05, 2008


COntinuous VAriable Quantum Information with Atoms and Light

"Unlike qubits, where one atom or particle carries the information, continuous variables (CV) use an ensemble of atoms or photons to carry the information – the first with matter and the second with light.

"Both digital and analogue approaches to quantum information science use the peculiar properties of quantum particles as the ‘signifier’ of the information carried, such as the spin of a single electron or the polarisation of a photon for qubits, or the analogue properties of a group of electrons or photons for CV.

It is the collective property of this group of electrons, or photons, that becomes the information carrier in CV. When you have this many particles you can call it continuous even though there are many very small steps in the information-encoding variable,”

The reason for the shift from digital to analog in processing quantum information is size as handling individual quibits (single photons, electrons etc., etc.) is really hard while handling millions of photons or atoms to spread out and manipulate the data is easy. Maybe this is why Carver Mead, the inventor of VLSI, loves analog (digital counts/analog measures) because it is "soft/energy efficient" and can be used in elegant ways with digital as seen in his Foveon X3 Image Sensor, exquisite hardware that "uses three layers of pixels embedded in silicon. The layers are positioned to take advantage of the fact that silicon absorbs different wavelengths of light to different depths. The bottom layer records red, the middle layer records green, and the top layer records blue. Each stack of pixels directly records all of the light at each point in the image."

By using analog techniques to process quantum information, the European researchers ..."created an optical ‘Schroedinger’s cat’. Schrödinger’s cat was a thought experiment that illustrated how objects can have two distinct states at the same time, in this case a dead cat and a live cat.

Covaqial created a light pulse – an ensemble of photons – simultaneously in two states."

and "interspecies quantum teleportation. Teleportation occurs where the state of one particle is moved onto another particle. “It had been done before with photons or atoms, but this is the first time it worked from photons to atoms.

The implications of this tech regarding quantum computing knows no bounds. At this point in time, this may be the best way to build practical QCs of unimaginable power.

Reality is digital with analog override - RM
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