6,099 reputation
1643
bio website jfitzsimons.org
location Singapore, Singapore
age 32
visits member for 3 years, 9 months
seen Dec 6 '13 at 16:11

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.


Aug
26
awarded  Nice Answer
Jul
3
awarded  Popular Question
Feb
3
awarded  Pundit
Jan
26
awarded  Nice Answer
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2
awarded  Popular Question
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20
awarded  Good Question
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26
awarded  Nice Answer
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5
awarded  Yearling
Nov
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comment Does entropy measure extractable work?
@WetSavannaAnimalakaRodVance Most of the work on this topic postdates Jayne's papers, so they are far from the last word on the subject. I'm not really sure what you mean by the "ensemble" being well defined. For any quantum system $p_i$ is well defined, since they are simply the eigenvalues of the density matrix.
Nov
3
comment Does entropy measure extractable work?
@WetSavannaAnimalakaRodVance: I'm afraid I don't see how this is related to the questions or answers. I don't believe any of us are discussing the ability to accurately infer entropy from measurements, but rather whether three concepts (work extraction, information theoretic entropy and physical entropy) are equivalent.
Nov
3
comment Does entropy measure extractable work?
@WetSavannaAnimalakaRodVance Sure, but something like the von Neumann entropy of a state is always defined. It doesn't depend on the system being in a Gibb's state, and hence doesn't require temperature to be defined.
Oct
9
comment What can the D-Wave quantum computer do?
@Blaisorblade: I meant that the converse can't be shown easily (i.e. that it is not NP-complete). Regarding noise, I use "noise" as a synonym of "decoherence".
Aug
17
comment The Many Body problem
@BenCrowell: Even for single atoms, I believe thulium is an example of a system where the ground state of the electrons is hard to find computationally.
Aug
17
comment The Many Body problem
@BenCrowell: None of what you have just said is an accurate description of the true situation. Being chaotic does not in any way mean a system is computationally difficult to simulate. Rather it means that the outcome of a simulation for one initial condition may diverge rapidly from a similar initial condition. That's what makes weather hard to predict, not that we can't numerically solve the equations. Secondly the bit about ground states is also inaccurate. The ground state of the transverse Ising Hamiltonian, for example, is computationally hard to solve.
Aug
2
awarded  Nice Answer
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31
awarded  Good Answer
May
31
comment What can the D-Wave quantum computer do?
@PeterShor: Indeed. I didn't mean to suggest that it was the only algorithm that works. It seems even trial division is possible with a few months and a few dozen GPUs on your hands.
Jan
24
awarded  research-level
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8
awarded  quantum-mechanics
Dec
29
awarded  Nice Answer