Modern Physics
5/10/11 Spring 2011
Ben Miller, Alexander DeCarli, Kevin Shaw
• 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 another
Einstein called this "Spooky action at a distance."
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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?
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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.
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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.
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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.
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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 used
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"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"
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- 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 spin
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Ben Miller
Alexander DeCarli
Kevin Shaw
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http://www.davidjarvis.ca/entanglement/quantumentanglement.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/200
7/02/d-wave-quantum-2.jpg
http://discovermagazine.com/2007/may/quantumleap/d-wave_processor2_lg.jpg
http://www.cpfreviews.com/PhotonProton/DCP_5238_Proton_Beam_McKinl.jpg
http://lightzombies.com/store/images/Photon%20II%20B
eam%20%20NVG.jpg
http://focus.aps.org/files/focus/v24/st11/freq_doubler.jp
g
Article on quantum entanglement at high
temperatures.
http://www.technologyreview.com/blog/arxiv/24797/