How stable/fragile is Quantum Entanglement?

In summary, Quantum Entanglement can work across large distances and is not affected by noise. However, it can be disrupted by measurement or detection. Entangled states can also be created by noise and can be used to make a qubit insensitive to certain types of noise. The usefulness and sensitivity to noise of an entangled state depends on its context. Additionally, the knowledge of individual systems can decrease, while the knowledge of the combined system remains maximal. It is also suggested that entangled particles may be connected in a different dimension, making them only observable as a unit. However, this is a topic of ongoing study and understanding in this field.
  • #1
San K
911
1
How stable/fragile is Quantum Entanglement? with respect to time, space and various events.Space - We know that experiments have validated QE working across say 150 kms and it is generally believed that they can work across very large distances. Does gravity effect QE over large distances?

Time - How long can Alice and Bob keep their entangled photons bouncing of mirrors? (if that is how entangled photons are kept trapped)

The interesting part is that between the two entangled photons there is so much background noise (in the form of EM radiations, other energy forms, matter and the various fundamental forces) yet entanglement survives.

Yet QE "breaks" as soon as we try to measure one of the twins and it's believed, by some, that the photons at that point get entangled with something else (like parts of the measurement apparatus).

It seems as if entangled particles are "connected" via a different mechanism/channel/dimension? and hence the noise does not effect them, yet events like measurement/detection does?
 
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  • #2
San K said:
It seems as if entangled particles are "connected" via a different mechanism/channel/dimension? and hence the noise does not effect them, yet events like measurement/detection does?

Are you sure that entanglement isn't affected by noise? In fact, entanglement is very sensitive to the effects of noise. In a finite time interval, some combinations of noise can even cause entanglement to drop to zero within a finite time - "entanglement sudden death" (Yu and Eberly, 2004)
 
  • #3
Fightfish said:
Are you sure that entanglement isn't affected by noise? In fact, entanglement is very sensitive to the effects of noise. In a finite time interval, some combinations of noise can even cause entanglement to drop to zero within a finite time - "entanglement sudden death" (Yu and Eberly, 2004)

ok, so entanglement is effected by noise. Now the question is what kind of things effect (and don't effect) quantum entanglement? Could this tell us more about the nature/properties of entanglement?
 
  • #4
If you are interested in finding out more about entanglement and have time, I refer you to this excellent review paper by the Horodecki family (yes, a whole family of physicists):
http://arxiv.org/abs/quant-ph/0702225
 
  • #5
San K said:
ok, so entanglement is effected by noise. Now the question is what kind of things effect (and don't effect) quantum entanglement? Could this tell us more about the nature/properties of entanglement?

"Entanglement" is actually a fairly broad term. While it is true that entanglement that is used for things like quantum computation is usually pretty fragile and easily disturbed by noise, this is not true for all entangled state. In fact, entangled states can also be used to make an otherwise sensitive qubit, completely insensitive to certain types of noise, by putting it in what is called a decoherence free subspace.

Also, some entangled states are even created BY noise, and can stay in this noisy environment indefinitely (see e.g. work by E. Polzik). However, one must remember that not all entangled states are useful in the sense of quantum computing and communication (think there was a paper by J. Eisert stating that most entangled states were not useful in fact), so the question of whether an entangled state is useful and how sensitive to noise it is, is very context dependent.
 
  • #6
Zarqon said:
"Entanglement" is actually a fairly broad term. While it is true that entanglement that is used for things like quantum computation is usually pretty fragile and easily disturbed by noise, this is not true for all entangled state. In fact, entangled states can also be used to make an otherwise sensitive qubit, completely insensitive to certain types of noise, by putting it in what is called a decoherence free subspace.

Also, some entangled states are even created BY noise, and can stay in this noisy environment indefinitely (see e.g. work by E. Polzik). However, one must remember that not all entangled states are useful in the sense of quantum computing and communication (think there was a paper by J. Eisert stating that most entangled states were not useful in fact), so the question of whether an entangled state is useful and how sensitive to noise it is, is very context dependent.

Interesting information. Thanks Zargon and Fightfish, I will go through the references, you provided.
 
  • #7
Schrodinger said " One disposes provisionally (untill the entanglement is resolved by actual observation) of only a common description of the two in that space of higher dimension. This is the reason that the knowledge of the individual systems can decline to the scientist, even to zero, while that of the combined system remains continually maximal. best possible knowledge of a whole does not include best possible knowledge of its parts - and this is what keeps coming back to haunt us"

What I think "Has it occurred to anyone that the two particles are getting entangled in a completely different dimension so that they are observable only as a unit and as soon as we try to study them as individual systems it should be zero as our instruments cannot detect any activity in those dimensions."

am I right or wrong please do help me understand as I am new in this field.
 

1. How does quantum entanglement work?

Quantum entanglement is a phenomenon in quantum mechanics where two or more particles become connected in such a way that the state of one particle is dependent on the state of the other, even if they are separated by large distances. This connection is known as entanglement and it occurs through the process of quantum superposition.

2. Is quantum entanglement a stable or fragile phenomenon?

Quantum entanglement is considered to be a very stable phenomenon. It has been observed in many experiments and has been shown to persist even over large distances. However, it is also fragile in the sense that any interaction with the entangled particles can cause the entanglement to be destroyed.

3. What factors can affect the stability of quantum entanglement?

There are several factors that can affect the stability of quantum entanglement. These include external interference from the environment, the physical properties of the particles involved, and the distance between the entangled particles. Additionally, interactions with other particles can also disrupt the entanglement.

4. Can quantum entanglement be used for communication?

No, quantum entanglement cannot be used for communication. While it may seem like entangled particles can communicate instantaneously, this is not the case. The information gained from measuring one entangled particle is random and cannot be controlled or manipulated, making it impossible to use for communication purposes.

5. What are the potential applications of quantum entanglement?

Quantum entanglement has potential applications in quantum computing, cryptography, and teleportation. It could also be used for secure communication, as any attempt to intercept or measure the entangled particles would disrupt the entanglement and be detectable. However, further research and development is needed before these applications can become a reality.

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