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422
bio website jessriedel.com
location Yorktown Heights, NY
age 29
visits member for 2 years, 8 months
seen yesterday

Physics postdoc at the Perimeter Institute. Interested in quantum information, consistent histories set selection, decoherence, and classically undetectable soft-particle detection.

Previous postdoc at IBM Research with Charlie Bennett. UCSB Physics Ph.D. 2012 (advisor: Wojciech Zurek). Princeton Physics B.A. 2007. TJHSST 2003.

http://www.jessriedel.com


Oct
15
comment Is the ground state of a QFT always a pure state? And excited states are mixed?
Said another way: the important distinction for getting area laws rather than extensive/volume scaling isn't so much pure vs. mixed, but rather local vs. random.
Oct
15
comment Is the ground state of a QFT always a pure state? And excited states are mixed?
The fact that the pure state under consideration is the ground state of a local Hamiltonian is crucial. A random pure state taken from the Hilbert space according to the Haar measure has extensive entropy (i.e. increasing proportional to volume until, of course, you reach the point where the region considered becomes as large as half the total system, at which point the the entropy scales like the volume of the complement region). This is Page's conjecture, later proved, and is a consequence of the concentration of measure. arxiv.org/abs/gr-qc/9305007
Oct
6
awarded  Excavator
Oct
6
revised A step in the derivation of the magnetic moment of the electron in Zee's QFT book
Fix typo in title. It's "magnetic moment" not "magnetic momentum", as confirmed by phrase used in the body.
Oct
6
suggested suggested edit on A step in the derivation of the magnetic moment of the electron in Zee's QFT book
Sep
20
awarded  Enlightened
Sep
20
awarded  Nice Answer
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.