Modern Physics 51011 Spring 2011 Ben Miller Alexander DeCarli Kevin Shaw What is it How do particles become Entangled Parametric Down Conversion A laser usually ultraviolet for its high frequency sends a photon through a nonlinear crystal such as Beta Barium Borate ID: 275323
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Slide1
Quantum Entanglement
Modern Physics
5/10/11
Spring 2011
Ben Miller, Alexander
DeCarli
, Kevin ShawSlide2
What is it?Slide3
How do particles become Entangled?Slide4
Parametric Down Conversion
A laser (usually ultraviolet for its high frequency) sends a photon through a nonlinear crystal such as Beta Barium Borate
The photon bumps an electron to an excited state
When the electron comes back down and releases its photon, there is a chance it will split
If it splits, the two photons are equally half of the energy
These two photons are entangled
The overlapping of the cones represents the entanglement
The two photons are also polarized opposite of one anotherSlide5
Einstein called this "
Spooky
action at a distance."
Slide6
What is the “spookiness?”
Bell-state Quantum Eraser
The split photons are opposite in polarization
The double-slit selectively filter between polarizations (e.g. right slit allows clockwise)
A filter in front of Detector A for polarizations as well
If the A filter restricts the polarized light, then the polarization entering the double-slit is known and no interference
If the A filter allows all light, then polarization entering the double-slit is not known and interference shows up in both detectors.
How do photons at B know that polarization is no longer restricted at A?Slide7
History
Quantum Entanglement comes from the ERP paradox paper.
The paper was written by Albert Einstein, Nathan Rosen and Boris
Podosky
in 1935.
ERP is a topic in physics concerned with measuring and describing microscopic systems.
The three men felt that quantum mechanical theory was incomplete.
By incomplete, they were talking about entanglement but did not have a name for it.
Slide8
More History
Erwin Schrodinger read this paper and wrote to Einstein talking about the idea and called it “entanglement.”
Schrodinger later wrote a paper that defined the idea of entanglement.
Both Einstein and Schrodinger were dissatisfied with the idea.
In 1964 entanglement was tested and disproved by John Bell because it violated certain systems but since then other experiments have proved it to be true.
Each experiment had its flaws though. Slide9
Applications
Quantum Communication
Quantum Teleportation
Quantum Cryptography
A quantum system in an entangled state can be used as a quantum information channel to perform tasks that are faster than classical systems.Slide10
Macroscopic observation
Typically
, entanglement experiments involve entangling pairs of photons and observing the changes in one effecting the changes in the
other
Italian
physicists thought of an idea where the effects of entanglement could be easily
detected
A
pair of photons could be entangled and then separated. One of the photons could then be amplified into a shower of thousands of other photons, all entangled to the lone other
photon
Nicolas Gisin from the University of Geneva in Switzerland decided to test this with humans
.
The
beam of macro
photons
could be shown in one of two positions on a wall depending on the polarization of the lone microscopic photon, which defined the group
.
The
human tests were successful and matched with the results of a photon
detector
A
flaw was discovered in which detection of the photon would still occur after the entanglement connection was supposedly broken, suggesting a flaw in amplification and the inherent flaws in any
detector
This
flaw also hints that this particular experiment may not have been a micro-macro entanglement condition, but work is being done to enhance amplification with
lasers
Clearly
, humans can not be
usedSlide11
Communication
"
Superdense
coding"
We
typically use bits in
computer
processing, or in this case, classical bits
In
Quantum Mechanics, information can be stored using qubits, which describe a quantum state
Information
can be obtained via measurement of the
qubit
In
theory,
qubits
can contain other
dimensions
of information, but the predictability of determining information is only completely effective on a 1:1 scale of information from classical to quantum
This
means that effectively, a
qubit
can only reliable store as much as a classical bit
Useless
? Not with entanglement.
Qubits
can be entangled in pairs and therefore two classical bits per
qubit can be reached.
This
is a doubling of efficiency known as "
superdense coding"Slide12
Teleportation
- Has to do with transmitting a
qubit
from one location to another without the
qubit
being moved through free space
- This can be used in the idea of a quantum computer, which would take advantage of changes in quantum states in order to rapidly send and process data
- With the
qubit's
use of other dimension, more advanced algorithms can be used, in theory, to solve specific problems significantly faster and more effective than any classical computer
- However, it is important to note that a classical computer can simulate a quantum one, therefore a quantum computer would not be able to solve a problem that a classical computer could not. - Typically, qubits
are used to define and alter particle spinSlide13
Your Welcome
Ben Miller
Alexander
DeCarli
Kevin ShawSlide14
Sources
http://www.davidjarvis.ca/entanglement/quantum-entanglement.shtml
http://www.technologyreview.com/blog/arxiv/24797/
http://en.wikipedia.org/wiki/Quantum_entanglement
http://plato.stanford.edu/entries/qt-entangle/
http://www.blogcdn.com/www.engadget.com/media/2007/02/d-wave-quantum-2.jpg
http://discovermagazine.com/2007/may/quantum-leap/d-wave_processor2_lg.jpg
http://www.cpfreviews.com/Photon-Proton/DCP_5238_Proton_Beam_McKinl.jpg
http://lightzombies.com/store/images/Photon%20II%20Beam%20%20NVG.jpg
http://focus.aps.org/files/focus/v24/st11/freq_doubler.jpgSlide15
Article
on quantum entanglement at high temperatures.
http://www.technologyreview.com/blog/arxiv/24797/