Joe Fitzsimons

5,666 reputation

1337

bio	website	jfitzsimons.org
	location	Singapore, Singapore
	age	31
visits	member for	2 years, 7 months
	seen	2 days ago
stats	profile views	470

I have just moved to the Center for Quantum Technologies in Singapore, after spending the last 3 years as a Merton College JRF in Theoretical Physics and a Senior Research Fellow in Oxford University Department of Materials. My research focuses largely on theoretical aspects of quantum information processing. In particular I am interested in spin networks, measurement based computation, cryptography and computational complexity.

	5,666 reputation	bio	website	jfitzsimons.org	visits	member for	2 years, 7 months
1337 badges		location	Singapore, Singapore		seen	2 days ago

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Jan 22	comment	Can gravitational potential energy be released in a fire? @Georg: Your objection is incorrect. As long as the same amount of fuel is burned, you are essentially dumping the same mass of gas into the atmosphere, whether at ground level, or at elevation. The effect of these new molecules falling on average, as they come into equilibrium with the atmosphere heats it.
Jan 22	comment	Don't heavier objects actually fall faster because they exert their own gravity? @Jerry: This isn't true in the earth's atmosphere, which is why people find it so counter intuitive in the case of a vacuum (a caveat which you should probably add).
Jan 22	comment	Transfer function of an RLC circuit This looks very like a homework problem, so I doubt you will find anyone to give you the answer here. For this reason I have also voted to close the question. However, I will point you in the right direction: What you are looking for is Kirchoff's laws (en.wikipedia.org/wiki/Kirchoff%27s_circuit_laws).
Jan 22	comment	Why does a ballerina speed up when she pulls in her arms? You're definitely better at expository answers +1.
Jan 22	comment	Double slit experiment near event horizon @kakemonsteret: Yes, I know it's only a practical consideration.
Jan 22	answered	Why does a ballerina speed up when she pulls in her arms?
Jan 22	comment	Double slit experiment near event horizon @Columbia: That is nonsense. The evaporation of the hole will effect the state inside the state sent in, so you are not violating the no-cloning theorem.
Jan 22	comment	Temperature of a System of molecules Actually temperature is usually defined as $T = (\frac{\partial S}{\partial E})^{-1}$, where $S$ is the entropy of the system.
Jan 22	answered	To calculate the correlation functions of an XX spin chain, Wick's theorem is used. But is it valid for a chain of any size?
Jan 22	answered	Is it possible to separate the poles of a magnet?
Jan 22	comment	Is it possible to separate the poles of a magnet? Monopoles are prohibited by Maxwell's equations, specifically $\nabla \cdot B = 0$. If you want monopoles you need to modify this particular equation.
Jan 22	comment	Double slit experiment near event horizon @kakemosteret: You won't make it across the event horizon anyway. The gradient of the gravitational field will rip you apart first.
Jan 22	comment	How can a photon have no mass and still travel at the speed of light? Exactly the answer I'd have given +1.
Jan 22	comment	Does decoherence need non-determinism? Good answer!
Jan 22	comment	Does decoherence need non-determinism? This isn't technically correct. Decoherence can be the result of an entirely deterministic (and unitary process), since you only care about the reduced density matrix for the system in question. Open quantum systems -do- decohere, even though the entire process is unitary. The larger wavefunction of the entire system is still pure, but the state of the local system becomes mixed.
Jan 21	revised	Does decoherence need non-determinism? added 807 characters in body
Jan 21	answered	Does decoherence need non-determinism?
Jan 21	answered	If a 1kg mass was accelerated close to the speed of light would it turn into a black hole?
Jan 20	revised	Using delayed choice interference experiments as a computing device deleted 2 characters in body
Jan 20	comment	Where's the best place to add weight to a Pinewood Derby car? @Mark: Sure, but since the question presumably relates to a real car, it it would be more reliable to simply measure them for the car in question.