6,215 reputation
11340
bio website lac.u-psud.fr/…
location Paris, France
age 38
visits member for 3 years, 8 months
seen 11 hours ago

Researcher in quantum information, mainly on cryptography.


Jun
20
comment Is there a cheap way I can do a Bell inequality experiment?
The most expensive part will be the single-photon detectors (a few 1,000$). Then, you cannot use two lasers because the photon would not be entangled. You need an entangled photon source (usually a suatably pumped BBO crystal)
Jun
20
reviewed Close Does time really exist?
Jun
19
comment Why isn't the best case classical solution to the CHSH game 100%?
@DavidZ I feel strongly about it, so I posted a question on meta.
Jun
17
comment Why isn't the best case classical solution to the CHSH game 100%?
The CHSH game has been invented by physicists to study a physics question (nonlocality). If you don't like to speak about games, call it the CHSH thought experiment!
May
28
awarded  Populist
May
28
comment Continuous Variable Entanglement Measure for the Statistically Mixed State
By the way, a review on entanglement measures is here : arxiv.org/abs/quant-ph/0504163
May
28
comment Continuous Variable Entanglement Measure for the Statistically Mixed State
It depends what you call valid. Logarithmic negativity always detect free (i.e. distillable) entanglement. But in high dimension, you have bound (i.e. undistillable) entangled states. These are entangled state with 0 log-negativity. But log-negativity is not invalid, since a non-zero negativity really means there is some entanglement, even in high dimension. Finding a “valid” entanglement measure, (detecing all entangled states) is essentially hopeless, since the probleme of entanglement detection has been linked to th NP problem.
May
28
comment Continuous Variable Entanglement Measure for the Statistically Mixed State
But if you only want a simple to compute entanglement measure, (logarithmic) negativity is your friend
May
28
comment Continuous Variable Entanglement Measure for the Statistically Mixed State
So a few questions : are you interested in the entanglement of a 2-mode system or a bigger one ? Do you want an entanglement witness or an entanglement measure ? Are your state supposed to be Gaussian or not ? Depending on your answer to these question, the answer could be different.
May
28
comment Continuous Variable Entanglement Measure for the Statistically Mixed State
Indeed, the von Neumann entropy of the reduced matrix is not an entanglement measure for statistically mixed states, since it is very high for the tensor product of two noisy states. In general, entanglement measures for statistically mixed state are plenty and have different physical meaning (e.g. entanglement of distillation is not the entanglement of formation, which is not the negativity, an so on.). So, your question does not have a single valid answer, because we do not know enough on your system and why you want to look at it's entanglement.
Jan
23
comment Resolution of the EPR paradox using special relativity
Your “solution” has many problem. The easiest to see is the fact that the EPR paradox is exactly the same with slow moving objects like neutrons and atoms.
Nov
12
awarded  Yearling
Oct
8
comment Why is Quantum Teleportation important in Cryptography?
@Martin : In what sense "very good" ? It is clearly secure, easy to analyse, but incredibly difficult to implement.
Oct
8
comment Why is Quantum Teleportation important in Cryptography?
Shifting the problem into something easier to analyse is the whole theoreticians work.
Oct
7
comment Do mirrors have a “resolution” quality to them?
That's for a perfect mirror. The rugosity of the mirror plays a role, and that's why astronomical mirrors are much better polished than a bathroom mirror !
Oct
7
comment Why is Quantum Teleportation important in Cryptography?
@Martin Done ;-)
Oct
7
answered Why is Quantum Teleportation important in Cryptography?
Oct
7
comment Why is Quantum Teleportation important in Cryptography?
@Martin Actually teleportation is essential in many security proof for quantum cryptography.
Oct
2
comment How can electrostatic forces provide lift to the gossamer spider?
If you have an electric field $\vec E$, it generates a force $\vec F=q\vec E$ on any object with charge $q$. A force, if it points upwards, is called lift. I don't understand your "but that's not an explanation about how it generates lift".
Oct
2
comment Coulomb force on the center of a hexagon?
Think about the symmetry of the problem. More specifically, look if some forces cancel out in the centre of the hexagon.