Entanglement Definition and 880 Threads

I just overheard an engineer saying "There are no two clocks in the world that tell identical time". She was describing a time syncing mechanism to another engineer, but it made me think... In theory, can something large enough to be used as a clock become fully entangled with a copy of...

In a nutshell I think that in local realistic theories it is assumed that: Each entangled object has definite properties at all times, even when not observed. I know the assumption is proved to be incorrect but is that an assumption actually made in such theories?But what assumptions about...

I have 2 questions i would really like to find an answer to: if we have a quantum pair, we can determine whether 2 quanta are entangled or not assuming that we have access to the information of both of them. so if we have a quantum "trio" instead of a quantum pair, does the information about 2...

Usually, people trying to explain quantum entanglement, uses the scenario where two particles were created and one of them ends up very far away from the other, and then a measurement is made, etc. The problem I see is that they seem to assume the two particles are classical particles, like two...

When two quantum objects interact, when does this interaction destroy their superposition and when does this interaction causes them to be entangled and allow the superposition to remain.

I've read that two electrons can become entangled in a "potential well," which is a point where potential energy is lowest compared to its surroundings. Is this correct? What does this have to do with entangling particles?

I have never heard a challenge by quantum entanglement to the concept that a state is a "property" of a particle, which I don't understand. I cannot see any way someone can interpret a state as a property of a system, rather than as a means of treating information about the system, given how...

I don't have much of a background in quantum physics so be patient with my questions please. Basically I want to know how does entanglement actually work? Is information being transferred faster than we can detect it or is there some invisible link between particles that causes the phenomenon we...

Specifically do we know how the two parties (photons) involved communicate ? how does the state information transferred. Is it transferred by some waves similar to radio waves ? I somehow still can not believe that its real.

In other words, it seems that if you have entanglement, then you have correlation (of measured properties). But is it true that if you have correlation, then you have quantum entanglement? Classically, correlation is between macro-events. But macro-events are made of micro-events. So is...

Two particle entanglement such as bell state measurement for quantum teleportation is the example commonly used and in fact you can find everywhere. I understand it like how maximal entanglement can mean measuring one you can know the property of the other.. but it is not very useful for...

I'm curious if any matter/antimatter or electron/positron entanglement is possible in theory or has been attempted?

I split this off a separate thread in response to a post of @Nugatory . The matter was about the (im)possibility of transfering information using entanglement. This is a basic thread, so I keep it simple: There are two particles/detectors, A and B. The particles are in the singlet state. My...

Hi ,I know that Entanglement arises naturally when two particles are created at the same point and instant in space." Therefore should not all particles in the universe have already been Entangled?have not they all created at the same spot?as they have all created in the big bang? and...

It is said that the measurement done on a particle instantly affects its entangled pair because Bell's theorem excludes a hidden variable. That means there is a cause and an instant effect at a distance. Say we have two entangled particles A and B. If there is no hidden variable then the state...

Nucleus are entangled to electrons... Atoms are entangled to other atoms in molecules.. Are molecules at distance also entangled to one another? Is there a way to test if this is true? I want to know if our biochemistry is entangled to the biochemistry of other people.

In classical mechanics, if a system consisting of one particle suddenly became two particles, the entropy of the system would increase because the number of spatial degrees of freedom would double. But, in QM, I believe, when one particle decays into two particles, the two new particles would be...

Could this be a possibility at some point? Since entanglement is not affected by distance, could we send cameras out to extremely distant places and get instantaneous signals? Only the image sensor would have to be entangled. It would still take the same amount of time as usual to get the camera...

If one beam from SPDC is sent to a double-slit or similar experiment, it can form interference if the which-way information is erased in the other beam. To detect it, photons have to be counted in coincidence because there will be both interference and "anti-interference" that add up to a...

Damn near gagged on my breakfast this morning when reading the last sentence in an article in Time Magazine by Jeffry Kluger (a "senior writer at Time Magazine") where he said: I know we've all seen this kind of horse manure before but that doesn't make it any more palatable.

The Bell inequality tells us (in effect) that if two photons (for example) were entangled when emitted, then we have a 50% chance of being able to detect that they were no longer entangled when they were received. To rephrase that, if they are not entangled when they are received, they still...

I am getting mixed messages on how fast entanglement is. Sometimes I am told it just happens instantly, sometimes it will say it is 10,000 times faster than light. I cannot comprehend how it can be instant because that would imply that if I change something in a quantum particle the change in...

Can teleportation possible through quantum entanglement??

ShayanJ submitted a new PF Insights post Entanglement Entropy – Part 2: Quantum Field Theory Continue reading the Original PF Insights Post.

Lets say a radioactive atom decayed into an alpha particle and a daughter nucleus. The two particles are entangled. If you measure, the alpha particle, you will collapse the wavefunction of the daughter nucleus. Other than collapsing wavefunction, does have any effect on the daughter nucleus?

This weeks Science frontpage article: Source: http://science.sciencemag.org/content/356/6343/1140

I joined this site because I had questions and wanted to discuss topics on the subject of black holes. Lenny Susskind's lecture of this topic raised quite a few question a and ideas in my mind. I did write my concerns in the comments for the video, but I'll just paste that here as well. Here's...

Came across a pair of websites claiming to be DIY Quantum Entanglement Experiment. Problem is, I don't know how realistic it is. Essentially, is this real, or am I being taken for a fool? Part 1...

I like this site because, even when people ask fundemenal questions ( bone headed ) they are not humiliated, lol, so hear I go. Could one use the mirror's left on the moon to observe quantum entanglement? Earth based laser, change phase on the way out, observe the returning photons?

Suppose we have two truly random sources A and B that generate bits ('0' or '1') synchronously. If we measure the correlation between the respective bits generated, we find a random, ie no, correlation. Now suppose A and B are two detectors that register polarization-entangled photons passing...

Wasn't sure whether to post this in SR or QP here, but chose the latter. Assuming: 1. The results of a quantum measurement are random, and that Alice and Bob (performing simultaneous measurements on widely separated, entangled particles) end up with measurements that are perfectly correlated...

Please forgive any misconceptions or grevious errors, quantum mechanics and relativistic physics is something I read and think about as a hobby and not a career. My question is this, does the entanglement or two particles transcend time difference? To expand, let's say we have two...

ShayanJ submitted a new PF Insights post Entanglement Entropy - Part 1: Quantum Mechanics Continue reading the Original PF Insights Post.

Hi. I wonder if following thought experiment (which is most probably impossible to be put into practice) could have any implications concerning interpretations of QM. Consider five parties A, B, C, D and E, lined up in that order and with no relevant relative motion. No pair of them have ever...

I've seen diagrams of quantum computer components at a high level that discusses multiplexing laser reflections over many qubits, and I have to believe that entanglement as a hardware operation has to be scaled to the many qubits by means of some operation that is applied to each of them...

Suppose we have an entanglement state between many qubits. When we measure this state anywhere, the entanglement is destroyed. In quantum computing, we have two bits of parity for each qubit, and we have to re-setup the entanglement state for each qubit to read each piece of information...

Hello, A photon can have various types of polarization states (horizontal, vertical, circular, elliptical, linear at an angle ##\theta##). Any valid polarization basis is two-dimensional and can represent any state of polarization. What are the actual eigenvectors of the polarization...

I'm having a little bit of trouble getting my head around the idea of the reduced density operator being used to tell us about the entanglement of a state. I understand that if you take the reduced density operator of any of the Bell states, you get a reduced density operator proportional to...

"To do this, the scientists turned the difficult analytical problem into an easy geometrical one. They showed that, in many cases, the amount of entanglement between states corresponds to the distance between two points on a Bloch sphere, which is basically a normal 3D sphere that physicists use...

So I'm working on a creative writing exercise, and I need some ideas. It's futuristic science fiction, set about 100 years in the future. The plot in a nutshell is that a rogue element of the government (think DARPA, only more evil) is trying to develop faster than light communication using...

The experiments that have been done to demonstrate that entangled particles are correlated (or anti-correlated) have been designed so that Alice and Bob's measurement events are intentionally space-like separated. Thus demonstrating that the "ghostly action at a distance" is supraluminal or...

I am not sure that I fully understand even the basic aspects of the Quantum measurement and entanglement but I just came across this thought experiment and I wish to resolve it. In a setting of two entangled spin-1/2 particles, suppose that Alice applies a uniform magnetic field ##B_0## along...

In an effort clarify confusion in my own mind on the definition of entanglement, I looked at wiki and found this: As an example of entanglement: a subatomic particle decays into an entangled pair of other particles. The decay events obey the various conservation laws, and as a result, the...

I rarely hear about momentum entanglement, do you know any experiments/applications for momentum entanglement? If we do momentum entanglement on 2 particles, and then we accelerate one of the particles, will the other particle slow down to obey conservation of momentum? or entanglement will be...

Lots of people have wondered about whether we can get FTL communication from entanglement. My question is slightly different. Is it impossible to get FTL communication out of entanglement? If it has been shown to be impossible, then we can shut off the entanglement-FTL avenue altogether and...

I have a trivial question: when measuring 2 entangled particles A and B, what should be the timing between the measurments to get correct results? In other words after measuring A how long can we wait before measuring B before its state changes?

Neill et al. 2016, Ergodic dynamics and thermalization in an isolated quantum system NB: For a more introductory version, phys.org ran a piece on this article last summer From my understanding entanglement is generally seen as purely a quantum phenomenon, while on the other hand chaos is...

What has confused me for a long time is the interaction between superposition and entanglement. That is, what happens when one member of a pair of entangled particles passes through a filter that selects for an observable that is incompatible to the observable in which the pair is entangled...

Hello, I had never heard of "entanglement" (in regards to particles) until today when I read an article on it in Discover Magazine (July-August 2016, p.68). I searched for and found several threads here, but were too advanced to understand and/or did not seem to address my questions below. BTW...

Reading about the early Quantum entanglement experiments by performed by Ernst Bleuler and H.L. Bradt and independently by R.C. Hanna in 1948, they basically used a pair of Geiger counters set around sodium22 and when an electron annihilation event occurred that produced a pair of photons the...