Month: August 2010

Quantum Minesweeper

If you are vaguely interested in quantum mechanics, you must check out the game Quantum Minesweeper. You might want to start with the video tutorial before you play online.

The game differs from classical Minesweeper in the following ways:

  • The board is really a quantum superposition of two boards. It is your goal to figure out the superpositions. It is simplified, as only one kind of phase is allowed.
  • There are three different kind of measurements that you can do, each one a limited number of times. The measurements are:
  1. classical measurement – collapse that can trigger a mine probabilistically. Very risky!
  2. entropy measurement – it indicates if there is a superposition or not, but doesn’t tell you if there is a mine or not!
  3. interaction-free measurements – it is very magical, doesn’t collapse the wave function, actually gives you the phase information. Very powerful!

This game is fantastic!

Technical digression:

I have a question that might be a good undergraduate research project for someone interested in quantum information. What is the optimal strategy for the game? That is, if you thought of this game as a kind of state tomography problem, is there a general protocol to extract the state with high fidelity, given the constrains of the number of measurements? To make it more interesting, imagine a version of quantum minesweeper where the boards could have between them any kind of phase, how much harder would solving it be?

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Give it one last try
til the next
one more
last try.
-A Wilhelm Scream

Dirac and Quantum Mechanics

Dirac invented quantum mechanics as we know it. He unified everything, adding much along the way into the modern formalism. His book from The Principles of Quantum Mechanics feels completely modern,although it was first published in 1930. However, he was also very humble, giving a lot of credit to others for things he himself discovered.

Kurt Gottfried posted a paper in arXiv:1006.4610 where he carefully examines the history of quantum mechanics by going to the original papers and getting the record straight. This highlights the central role Dirac played through out this. This cute paper is nice, with tons of references, some fun anecdotes, and just enough equations to get the details right. I highly recommend it.

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Time flies like an arrow. Fruit flies like a banana.
-Groucho Marx

Sudarshan gets the Dirac Medal

On Dirac’s birthday, I would like to congratulate E.C. George Sudarshan, for being awarded the Dirac Medal! George is one of the most important physicists of the last 60 years, whose work includes the discovery of the weak interaction (one of the four forces of nature), the formulation of the diagonal representation of quantum optics (discovering the “quantum” in optics), the discovery of the quantum Zeno effect (a watched pot never boils), the theoretical formulation of the faster-than-light particles called tachyons (take that Einstein) and the development of the foundations of open quantum systems (my personal favorite, as I did my Ph.D. with him on this subject).

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John McClane: Yippie-ki-yay!

Radiation, Boo!

New Scientist has an article, Who’s afraid of radiation?, with an overview of the history of regulation of radiation dosage and its impact on human health. It works as a nice follow up to my own post The Nucular Family.

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Radio does not, in general, go around corners. This can be a real pain when you are conquering the world, which is inconveniently round, placing all of your most active military units over the horizon.
-Cryptonomicon