Linked by Thom Holwerda on Fri 22nd Mar 2013 10:02 UTC
"But a powerful new type of computer that is about to be commercially deployed by a major American military contractor is taking computing into the strange, subatomic realm of quantum mechanics. In that infinitesimal neighborhood, common sense logic no longer seems to apply. A one can be a one, or it can be a one and a zero and everything in between - all at the same time. [...] Now, Lockheed Martin - which bought an early version of such a computer from the Canadian company D-Wave Systems two years ago - is confident enough in the technology to upgrade it to commercial scale, becoming the first company to use quantum computing as part of its business." I always get a bit skeptical whenever I hear the words 'quantum computing', but according to NewScientist, this is pretty legit.
by Bill Shooter of Bul on Fri 22nd Mar 2013 14:47 UTC

Member since:
2006-07-14

This is from the article in the New York Times, so I can hardly blame Thom for repeating it verbatim. But this is so freaking wrong it makes my head explode.

A one can be a one, or it can be a one and a zero and everything in between — all at the same time.

A one can be one or a zero or both. Not everything in between. It can't be a floating point 0.48294302. Quantum means a small discrete value.

Member since:
2010-10-27

A one can be one or a zero or both. Not everything in between. It can't be a floating point 0.48294302. Quantum means a small discrete value.

It's been artlessly stated, but there's more than a grain of accuracy in that line. A qubit can have a range of possible values; the basic values it can assume are zero or one. Physicists would say that the qubit (let's call it |q>) can be in either the state |0> or the state |1>.

However, it can also be in a linear superposition of these states. Given any two complex numbers c and d, the qubit can be scaled to become:

|q> = c|0> + d|1>.

There are normalization requirements to make the probabilities sum to unity but this is just really basic linear algebra on a complex vector space. It's in this sense, the sense of a continuous range of possibilities for the superposition over basis vectors that I take the quote you mention to refer. In which case he's entirely accurate, if admittedly a little unclear.

Edited 2013-03-22 15:55 UTC

Member since:
2006-07-14

Ok, I understand what you mean, and that's probably what they started from, but I disagree that the statement as written is accurate.

Member since:
2005-07-12

It is only a one AND zero until you test for it, at which case it becomes a one OR zero, and you only get a probabilistic value of it being a one or zero.

That's how it works, right?
Farking QM. Completely unintuitive.

Member since:
2009-03-17

The sentence could very well be correct, actually. Qubits, the basic unit of "information" in quantum computing, are quaternary in nature. As opposed to "traditional" digital bits, which are binary.

So a Qubit can be indeed, 0, or 1, or 0 and 1 simultaneously, or numerical coefficients representing the probability of each state.

Member since:
2010-10-27

The sentence could very well be correct, actually. Qubits, the basic unit of "information" in quantum computing, are quaternary in nature. As opposed to "traditional" digital bits, which are binary.

Qubits are not quaternions (or indeed "quaternary"). There exists an interpretation of quantum information theory using a quaternion formalism that eventually leads to something called density operator theory, but this is obscure even for the field.

So a Qubit can be indeed, 0, or 1, or 0 and 1 simultaneously, or numerical coefficients representing the probability of each state.

No. A qubit is a linear superposition of basis vectors in some two-dimensional complex vector space. Numerical factors representing probabilities occur only when one performs an operation on qubits (specifically the inner product on the vector space).