Reputation
3,976
Next privilege 5,000 Rep.
Approve tag wiki edits
Badges
2 16 23
Newest
 Marshal
Impact
~20k people reached

32m
comment Relating purity of reduced density matrix to concurrence
It is the trace of the square of the red. density matrix. Also, you should use that $|\alpha|^2+|\beta|^2=1$. Then, you can easily see that the two are equal!
7h
comment Relating purity of reduced density matrix to concurrence
What have you tried? Do you know how $C$ is defined? (It's a property of a two-qubit state!)
2d
comment reconstruct the wave-function from one body reduced density matrix?
@MikaelKuisma Doesn't the Hohenberg-Kohn theorem require that the state is a ground state of a very special Hamiltonian -- one which is uniquely fixed except for a one-particle potential (which only couples to the one-particle density), such as in the case of interacting electrons in an external potential?
Apr
28
revised Lowest energy product state of a local hamiltonian
edited body
Apr
28
revised Exponential decay of correlation in PEPS
added 605 characters in body
Apr
28
answered Lowest energy product state of a local hamiltonian
Apr
28
answered Exponential decay of correlation in PEPS
Apr
28
comment Complexity of quantum simulation
@CuriousOne Basically, any quantum mechanical problem can be simulated classically using a polynomial amount of memory (basically, using a path integral), a class known as PSPACE. It is not known whether PSPACE is strictly larger than P. So if you could prove for a quantum problem that it is outside P, you would have also solved a long-standing open problem in complexity theory.
Apr
27
comment Can particle quantum spin be described with a wave function?
"spin up" and "spin down" can be understood as completely classical properties. We're not talking about relativistic QM here -- it's just another property of an object, such as its position.
Apr
27
comment Can particle quantum spin be described with a wave function?
A wave function assigns to each possible classical state (such as position, or position and spin) of a particle a complex number.
Apr
24
comment Can particle quantum spin be described with a wave function?
Of course spin is characterized by the wave function. It is just a wave function defined on a spatial and a spin degree of freedom.
Apr
19
comment Trace of an observable
@B.Reddy In more detail? Unlikely.
Apr
19
revised Trace of an observable
added 19 characters in body
Apr
19
comment Trace of an observable
As it's written, the answer is no. Could it be that one of the $z$'s should be compex conjugated?
Apr
18
comment What do operations on single Qubits of Unfactorable Superpositions Do?
@DavidZ +1 for the fact that the question would be much more clear if most of it would be removed.
Apr
17
reviewed Close Space time curvature and gravity
Apr
16
comment Measuring qubit as the presence or absence of a particle
Note that encoding information in presence/absense of particles causes problems due to superselection rules (e.g., superpositions of particles typically cannot be created). This is not true for photons, but a similar problem might arise due to the lack of a phase reference. There are quite a few things which can be said about quantum information in the presence of superselection rules.
Apr
16
comment Measuring qubit as the presence or absence of a particle
What does "What sense does it make for that qubit" even mean? The qubit does not have a feeling of sense.
Apr
15
comment Quantum computing entanglement dimensions question
I think we strongly disagree.
Apr
14
comment Quantum computing entanglement dimensions question
So following wikipedia, the number of parameters needed to describe a mixed state is different from the number of parameters needed to describe the description of a mixed state? :-o