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bio website jessriedel.com
location Yorktown Heights, NY
age 29
visits member for 2 years, 6 months
seen 2 days ago

Physics post-doc at IBM Watson research center in Yorktown Heights, NY. Interested in quantum information, foundations, and decoherence. And maybe dark matter.

Ph.D. UCSB Physics 2012 (advisor: Wojciech Zurek). B.A. Princeton Physics 2007. TJHSST 2003.


Sep
12
revised Tensor Product of a Bra and a Ket
spelling
Sep
8
comment Why we never observe superposition of up and down ferromagnetic ground state of Ising model?
The up-down state does have special properties (long range entanglement), but it's also true that more realistic sources of environmental perturbations will do more than simple decohere. I've revised my responde, so let me know if it answers your question.
Sep
8
revised Why we never observe superposition of up and down ferromagnetic ground state of Ising model?
added 2514 characters in body
Sep
8
comment Tensor Product of a Bra and a Ket
Yes, the choice of order is just notation.
Sep
8
comment Tensor Product of a Bra and a Ket
Not quite, assuming I'm understanding you correctly. The tensor product of two vector spaces is another vector space. The members of this new, larger space aren't yet a linear map to scalars until you either (1) define an inner product (in which case the large vectors can map themselves to scalars) or (2) define a space of large covectors (in which case the vectors map covectors to scalars, and the covectors map vectors to scalars). Remember, a covector literally is a linear map from a vector space to the scalars.
Sep
8
revised Tensor Product of a Bra and a Ket
added 155 characters in body
Sep
8
comment Tensor Product of a Bra and a Ket
FYI, the issue with Hunter's notes is that they don't define covectors.
Sep
8
answered Tensor Product of a Bra and a Ket
Sep
8
comment Tensor Product of a Bra and a Ket
This type of question arises often when people are introduced to tensor products of vectors spaces in a physics context without taking a formal math class. (I know, because I had the same confusion.) I'll try to answer below.
Sep
3
answered Why we never observe superposition of up and down ferromagnetic ground state of Ising model?
Aug
9
comment Can “vacuum be brought” from outer space?
Thanks. This is the recent (2009) microsatellite stuff I alluded to. But note that this doesn't include reentry. I've never seen a good write up about the minimal vehicle size for reentry. Would love to know what's been done.
Aug
9
comment Can “vacuum be brought” from outer space?
Jim, it would be great if you could link us to a description of a similar mission (take a few kg to LEO and then bring it back to Earth) that cost less than $1 million.
Aug
9
comment Can “vacuum be brought” from outer space?
It's \$10k/kg, but that doesn't mean you can put 10 kg in orbit for $100k. There are fixed costs, and rockets have certain minimum sizes (generally with payloads that are many thousands of kilos). Such low costs may be possible with recent attempts with shared launches for microsatellites, but remember that you need a re-entry vehicle. I don't know if there are any that are so light.
Aug
9
comment Can “vacuum be brought” from outer space?
Many of the answers so far are getting hung up about the cost. learner didn't ask what the cost is, and there are plenty of interesting things to be learned by considering this as pure thought experiment.
Aug
9
answered Can “vacuum be brought” from outer space?
Jul
25
revised an example of a quantum system for which wigner function transitions to negative values
added 330 characters in body
Jul
25
awarded  Revival
Jul
25
comment an example of a quantum system for which wigner function transitions to negative values
You're off by a 45 degree rotation in your definition of the Wigner function. The usual notation is that $\rho(x_1,x_2) = \langle x_1 | \rho | x_2 \rangle$. In this case, the Wigner function is the result of Fourier transforming $\rho(x+\Delta x/2,x-\Delta x/2)$ with respect to the variable $\Delta x$, not $\rho(x_1,x_2)$ with respect to $x_2$.
Jul
25
answered an example of a quantum system for which wigner function transitions to negative values
Jul
25
comment Wigner characteristic function
I gave an intuitive discussion of the Wigner quasiprobability distribution on my blog: blog.jessriedel.com/2014/04/01/…