## Archive for the ‘Quantum-Computing’ Category

### Video: Delayed Choice Quantum Eraser Experiment Explained

Wednesday, June 24th, 2015

### Video: Google TechTalk: Designing a SuperConducting Quantum Computer – With XMONS

Wednesday, September 24th, 2014

### Delayed Choice Quantum Eraser Experiment Explained

Saturday, August 2nd, 2014

### Quantum Computing: Googles Quantum Computer Playground

Sunday, June 8th, 2014

Google has an online quantum computer simulator.  It has ready made simulation scripts for Shor and Grover's algorithm.  It allows you to enter your own scripts and save / recall them.

### Quantum Logic

Saturday, June 7th, 2014

### Quantum logic

In a famous paper of 1936, the first work ever to introduce quantum logics,[28] von Neumann first proved that quantum mechanics requires a propositional calculus substantially different from all classical logics and rigorously isolated a new algebraic structure for quantum logics. The concept of creating a propositional calculus for quantum logic was first outlined in a short section in von Neumann's 1932 work. But in 1936, the need for the new propositional calculus was demonstrated through several proofs. For example, photons cannot pass through two successive filters which are polarized perpendicularly (e.g., one horizontally and the other vertically), and therefore, a fortiori, it cannot pass if a third filter polarized diagonally is added to the other two, either before or after them in the succession. But if the third filter is added in between the other two, the photons will indeed pass through. And this experimental fact is translatable into logic as the non-commutativity of conjunction $(A\land B)\ne (B\land A)$. It was also demonstrated that the laws of distribution of classical logic, $P\lor(Q\land R)=(P\lor Q)\land(P\lor R)$ and $P\land (Q\lor R)=(P\land Q)\lor(P\land R)$, are not valid for quantum theory. The reason for this is that a quantum disjunction, unlike the case for classical disjunction, can be true even when both of the disjuncts are false and this is, in turn, attributable to the fact that it is frequently the case, in quantum mechanics, that a pair of alternatives are semantically determinate, while each of its members are necessarily indeterminate. This latter property can be illustrated by a simple example. Suppose we are dealing with particles (such as electrons) of semi-integral spin (angular momentum) for which there are only two possible values: positive or negative. Then, a principle of indetermination establishes that the spin, relative to two different directions (e.g., x and y) results in a pair of incompatible quantities. Suppose that the state ɸ of a certain electron verifies the proposition "the spin of the electron in the x direction is positive." By the principle of indeterminacy, the value of the spin in the direction y will be completely indeterminate for ɸ. Hence, ɸ can verify neither the proposition "the spin in the direction of y is positive" nor the proposition "the spin in the direction of y is negative." Nevertheless, the disjunction of the propositions "the spin in the direction of y is positive or the spin in the direction of y is negative" must be true for ɸ. In the case of distribution, it is therefore possible to have a situation in which $A \land (B\lor C)= A\land 1 = A$, while $(A\land B)\lor (A\land C)=0\lor 0=0$.

Von Neumann proposes to replace classical logics, with a logic constructed in orthomodular lattices, (isomorphic to the lattice of subspaces of the Hilbert space of a given physical system).[29]

### Video:Seth Lloyd on Quantum Life

Tuesday, June 3rd, 2014

### Video: Google TechTalk: John Preskill: Quantum Computing and the Entanglement Frontier

Friday, May 16th, 2014

Near the beginning of the video a crucial point is made.  Either of 2 quantum bits by itself does not store any data.  It is the correlation between the two bits that hold the data.

Do not forget to wear your quantum sockes.

### Two Bit Quantum Computer online

Sunday, September 15th, 2013

Once you understand the simulation you can ask permission to use the real thing. I guess that that will not be necessary because the simulation does the same thing.

### Video: Quantum Computation simulations using Mathematica and Free Quantum Computing Add On

Sunday, February 12th, 2012

This calculations are available at:   http://homepage.cem.itesm.mx/lgomez/quantum/v7phase.pdf

Shor's Factoring Algorithm is very important because it showed that a Quantum Computer will be more efficient than a normal computer when solving some important, practical problems (Factorization is important in the secure transmision of electronic data, like credit card numbers). This video shows briefly how Shor's algorithm can be simulated in Mathematica using the free Quantum add-on. Quantum is available at:  http://homepage.cem.itesm.mx/lgomez/quantum/

More  videos on related topics from the same author

### Video: Erann Gats explanation of quantum entanglement, measurement and interpretations

Thursday, December 22nd, 2011

Polarizer material experiment @ see 15:00 to 16:00 into the video below

—– 0 deg |  —- 90 deg | = nothing comes out.

—– 45 deg | —– 0 deg |  —– 90 deg | = ~nothing comes out.  I am calling the leakage "0"

—– 0 deg |  —– 90 deg | —– 45 deg | = ~nothing comes out.

—– 0 deg | —– 45 deg | —– 90 deg |  = 1/4 intensity

1/4 intensity is due to electric field vector being diminished 2 times by square root of 2. Electric field is thus 1/2 and intensity will be the square of this at a value of 1/4.

Later in the talk Garrett uses a polarization rotator. This takes the output of one orthogonal polarizer and spins it 90 degrees so that it aligns with the second polarizer giving no relative loss to a single sheet of polarizer material.  A single sheet of course has a loss of 1/2 when fed with unpolarized light. See image below.

David Mermin's "Stuff Left Behind" in terms of Von Neuman entropy.

I highly recommend you watch David Mermin's "Stuff Left Behind" presentation before you watch this presentation.  Mermin's work is like chapter 1 and this is like chapter 2.

Ron Garrett aka Erann Gat quantum video on quantum mechanics.   It helps make quantum mechanics more clear by using very accessible experiments that use light as the test subject.

Von Neumann Entropy

Where lambda are eigenvalues of the system.  Very similar to Shannon entropy but I suppose with complex values.

Notes

• The polarizer experiments that he shows are quite interesting.
• This  presentation builds on David Mermin presentation is like a second chapter to that
• The 3 particle correlation shown near the end is the David Mermin "Stuff Left Behind" presentation

Transcript