Recent content by slyboy

A superposition of gaussian states is not itself a gaussian state.

As far as I know, the transactional interpretation has never been worked out for a multiparticle system. It is hard to do because Cramer's ideas rely heavily on thinking about the wavefunction as a wave in ordinary 3-d space rather than configuration space. Thus is is better to think of the...

This is not quite right. There is a perfectly good way of describing things in which this does not happen. The point is to notice that there is an isomorphism between preparations and measurements in quantum theory, so we can obtain a perfectly retrodictive formalism by interchanging their...

Bell-tests are not just tests of local realism Careful, there is a big difference between experiments designed to test QM against local realistic theories and experiments that are just aimed at making progress towards scalable quantum information processing. Both types of experiment require...

It is worth noting that any hidden variable theory is required to be contextual in this sense due to the Bell-Kochen-Specker Theorem. In fact, violations of Bell's inequality are also a kind of contextuality, since the result of measuring an operator at one location has to depend on the...

P(B+, a) = P(B+, c) is definitely true in Bohmian mechanics for equilibrium ensembles. However, I think you need P(B+| a, \lambda) = P(B+| c,\lambda) to derive the Bell inequalities, i.e. you have to condition on the hidden state as well as the measurement settings. This is definitely...

Even two particle entanglement is a bit more interesting than your description suggests. In a maximally entangled state there is perfect correlation or ant-correlation between the particles, but other states can be entangled as well without perfect correlation or anti-correlation (in the sense...

This can work only for single particle wavefunctions and in fact was the original idea of de Broglie. There it is possible to think of the particle as being like a cork floating on water being pushed around by waves, via the de Broglie-Bohm interpretation of quantum theory. However, the...

I like "The Quantum Universe" by Tony Hey and Patrick Walters. The math is specifically aimed at high-school level and it is full of pictures. It really gives a feel for what doing quantum experiments is like and gives lots of applications. Of course, Schroedinger's cat et. al. also make an...

I think this is mistaken. Quantum computing is both a hardware and a software thing. In fact, it is a completely new way of thinking about information processing. Although you are right to say that quantum computations can be simulated on a regular PC by doing lots of matrix...

Wow, somebody was listening!

\left | \psi \right \rangle latex \left | \psi \right \rangle /latex \left \langle \psi \right | latex \left \langle \psi \right | /latex \left \langle \psi \right. \left | \psi \right \rangle latex \left \langle \psi \right. \left | \psi \right \rangle /latex Note: The...

Transactional Interpretation The basic problem with the transactional interpretation is that it only really works for single particle wavefunctions. It regards the wavefunction as a real wave in 3-dimensional space, but for multiple particles the wavefunction exists on configuration space...

Philosophy vs. physics Most of the better technical books on the interpretation of quantum theory tend to be written by philosophers rather than physicists (although there are quite a number of bad books by philosophers as well). I suppose this is because they are trained to consider every...

Some other good papers on Bell's theorem Quantum mechanics, local realistic theories, and Lorentz-invariant realistic theories Hardy L PHYS REV LETT 68: (20) 2981-2984 MAY 18 1992 "The mystery of the quantum cakes," P.G. Kwiat and L. Hardy, Am. J. Phys. 68, 33 (2000). "Hidden Variables...