Suppose Alice and Bob perform a test of a Bell inequality. They start together and produce an entangled quantum state. Then the parties move apart such that when they make their measurements on the entangle quantum state they are spacelike separated and are at rest with respect to each other’s motion. Let’s suppose that Alice and Bob perform their measurements at the same time (simultaneous) according to the two party’s rest frames. Now the standard paradox arises: the correlations Alice and Bob produce cannot be explained by a local hidden variable model: one party needs to produce an outcome which is predicated on the measurement choosen by the other party. So this seems very bad: if Alice sends a signal to Bob at the speed of light, immediately as she does her measurement, then the signal will arive at Bob at a time equal to the distance between the parties divided by the speed of light. But now look at exactly just this scenario from the perspective of a party who is traveling in a reference frame which is moving with a velocity in the same direction as the separation of Alice and Bob. If this frame is moving at nearly the speed of light with respect to rest frame of the parties, then the paradox seems almost triffling: in this frame of reference, Bob would get the information immediately after he would normally need it. Extrapolating as this party’s frame’s velocity goes to the speed of light and thinking that there is a limit to how sharply we can define when a measurement occurs, we see that “There exists a reference frame in which the paradox of Bell violation for all practical purposes disappears.”
What does this tell us? Well it certainly doesn’t resolve the Bell paradox. One thing to get is that the paradox is reference dependent. OK, not too interesting either. But what I think is neat about this thought experiment is it gives us a point of little or no paradox upon which we can begin to think about how to bootstrap our way into the reference frame where there is a very measurable Bell paradox. How do we do this? Heck if I know: the point is mostly that the solution should be a SMOOTH map from this little or no paradox reference frame to the frame where the information propogation is ridiculous.
A Koan
Email from a master:
Two theorists were walking through the forest of quantum mechanics.There they came across an ATM machine.
In front of the ATM machine was a long line of experimentalists.
The student asked,
“Surely master an ATM machine deep in the forest of Quantum Mechanics must have an incredible surcharge.”
The master,
“Can the hive steal money from a single bee?”
The student
“Without the bees, there is no hive.”
The master,
“Without the hive, there are no bees”
The student
“This honey is bitter”
The master,
“Fear not, we are not bees.
Blue Buddha
Today I learned that they offered the job I interviewed for in Vancouver to “an experimentalist.” Today is Buddha Day. Repeat after me: “I will not lose my Zen-Buddha nature, I will not lose my Zen-Buddha nature…”
Far more marvelous is the truth
The Physical Review response of a few days ago reminded me of this favorite quote, part of which I read at at the celebration we had after my dad passed away,
Poets say science takes away from the beauty of the stars — mere gobs of gas atoms. Nothing is “mere.” I too can see the stars on a desert night, and feel them. But do I see less or more? The vastness of the heavens stretches my imagination — stuck on this carousel my little eye can catch one-million-year-old light. A vast pattern — of which I am a part — perhaps my stuff was belched from some forgotten star, as one is belching there. Or see them with the greater eye of Palomar, rushing all apart from some common starting point when they were perhaps all together. What is the pattern, or the meaning, or the why? It does not do harm to the mystery to know a little about it. For far more marvelous is the truth than any artists of the past imagined! Why do the poets of the present not speak of it? What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent? – R.P. Feynman
Radiohead Lyrics
Radiohead sings “Just cos you feel it doesn’t mean it’s there.” But Descrates says “I think therefore I am.” Time marches on, old ideas die, and Radiohead pines a new philosophy.
Physical Review Editors
Here is a final paragraph I wrote (CTC = closed timelike curve):
Finally, we would not be honest if we did not end this paper with the caveat that this work is at best a creature of eager speculation. Without a theory of quantum gravity, we cannot know whether CTCs can exist let alone whether they can be generated within the confines of the such a theory. Practical considerations are humorous at best. The surprising answer that quantum computation in the presence of CTCs is a powerful new model of quantum computation gives us reason, however, to pause and ponder the implications.
and the Physical Review editors replied with:
The wording of the last paragraph of your paper does not conform to the presentation of Physical Review A. We prefer literal descriptions and suggest the following: End the first sentence with “… at best based on eager speculation.” Remove the penultimate sentence entirely.
Is it any wonder that science is full of dull writing and that the public’s perception of science is that of a bunch of boring egomaniacs jargonizing endlessly about trivialities?
Driving
From a distance, the words on the truck ahead say “Walmart,” “Always,” and “Less.” Word.
BC
The trip to Vancouver: a full plane with lots of smiles. “Heading home?” they would ask. “No,” I could only envy. From Vancouver at night you can see the lights from the local ski areas. “Nobody seems to leave UBC,” the faculty tell me.
The trip from Vancouver: a 20% full plane with lots of sleepers. And then there was the 1 1/2 drive back to South Pasadena. At night in LA you can sometimes see the moon if the smog isn’t too dense.
I have seen the promised land and it is good. Whether I am saint enough to ascend to such heights remains an open question. Any supersticious acts performed on my behalf will be duly noted in my big book of karma.
Job Talks
Job talks in the next few weeks, so I have been wandering around looking for advice. Here is a nice, calming quote from the Chronicle of Higher Education:
As a doctoral student or postdoc seeking a professorship, your academic job talk may well be the most important presentation you will ever give. An excellent talk can get you the job, while a poor one will almost surely eliminate you from contention.
No pressure, eh?
Through a CTO's Eyes
Pat Gelsinger, Intel’s CTO, on quantum computing from this interview:
For nearly a decade there has been talk about the coming quantum computing revolution, yet it seems no nearer. What is it that is causing the delay?
It will probably be talked about for another decade too. It certainly won’t be relevant for another decade. That doesn’t mean it’s bad research but it’s far from coming to the commercial sphere. We need to challenge some of the assumptions about quantum computing and what it will be used for. We’re now building 3bit quantum computers with possibly a 5bit one under construction. That’s fine, but I’m already building 64bit computers. When we get quantum to 14bit then it can be used for encryption, which is one of the key applications for it. The country that gets a quantum network first will have a real competitive advantage.
I wish I had a 3 bit quantum computer in the same sense that he has a 64 bit computer! I wonder, however, where his 14 bit claim comes from?