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11 votes

Does entanglement allow enhanced communication efficiency?

First, about teleportation, you say that you think quantum communication takes place in the protocol, but it doesn't. They only share an EPR pair they created together, hence the coordination and ...
Lena's user avatar
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9 votes
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Why does quantum distinguishability ensure no faster-than-light communication?

In the situation described in the book, Alice and Bob share the state $$ |\psi\rangle = \frac{|00\rangle+|11\rangle}{\sqrt{2}}. $$ Using the definition $|\pm\rangle=(|0\rangle\pm|1\rangle)/\sqrt2$ and ...
Adam Zalcman's user avatar
7 votes
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Quantum entanglement for faster-than-light (FTL) network communication?

As this is one of the first examples in Nielsen & Chuang, I'll go ahead and type out their explanation here for anyone else that is interested in entanglement for faster than light communication. ...
Andrew O's user avatar
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5 votes
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Can we teleport a human or send information faster than light using quantum teleportation?

In conclusion, NO and NO, respectively. Quantum teleportation does not mean instantaneous disappearance and reappearance of information at another spatial point. Quantum teleportation in plain ...
Siddhant Singh's user avatar
5 votes
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Does the Lieb-Robinson bound constrain the speed of entanglement information transmission?

Entanglement does not transmit information, as follows from the No-communication theorem. Lieb-Robinson bound is a limit on speed at which perturbation propagates using short-range interactions, for ...
kludg's user avatar
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4 votes

Why can't we use a two-qubit entangled state to send information faster than light?

The state that you start with can be written as $(|0\rangle+|1\rangle)\otimes (|0\rangle+|1\rangle)$. This means it is separable. Nothing you do on the first qubit will ever change anything on the ...
DaftWullie's user avatar
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4 votes
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Can joint measurement be achieved in two labs far apart?

TL;DR No. Non-local gates and measurements between causally disconnected observers violate the no-signalling theorem and are therefore impossible. No-signalling theorem The following protocol allows ...
Adam Zalcman's user avatar
3 votes

Faster than light data transmission using entanglement

No, you cannot use this for faster than light communication. The two typical ways that people think this could work are: Alice measures her qubit in a fixed basis, creating an instantaneous change in ...
DaftWullie's user avatar
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3 votes

Does entanglement allow enhanced communication efficiency?

It sounds like the source of your misunderstanding is the following Bob is able to harness the information of a qubit which contains more information than regular classical bits This statement is ...
rnva's user avatar
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3 votes
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Quantum indistinguishability using density operators

The mistake occurs when you compute the reduced state on Alice2's system. For simplicity we'll assume all systems are qubits and in addition $|x\rangle = |0\rangle$. In this setting, Bob2 prepares the ...
Rammus's user avatar
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3 votes
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Hypothesis on faster-than-light communication

If Alice is performing a CNOT on her and Bobs qubits, Bob (and his qubit) will need to be close to Alice. No matter how they prepare the state, once they are separated, local operations will not ...
john's user avatar
  • 46
3 votes

Does measurement in different bases allow for FTL communication?

If Alice measures in the $|+ \rangle$, $| - \rangle$ basis, then Bob's qubit will indeed be in either the $|+\rangle$ or $|-\rangle$ state depending on the result of Alice's measurement. But your ...
Nick Mertes's user avatar
1 vote

Why can't we use a two-qubit entangled state to send information faster than light?

Following your edit, I'll just clarify some things (and to just back-up @DaftWullie's answer and the comments). The final state is (following edit2): $$ |\psi\rangle = \begin{bmatrix} \frac{1}{\sqrt{...
banercat's user avatar
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1 vote

Superluminal communication via entanglement transceivers

The root misconception is the idea that an entangled particle somehow reacts when its partner is measured. It doesn't. Nothing changes, either faster than light or slower than light. The idea that it ...
Mateus Araújo's user avatar
1 vote

Superluminal communication via entanglement transceivers

The problem is that there's no way to definitively say what state each qubit started in if they were entangled, so there's no way to even establish what it means for one qubit to "change." ...
Quantum Mechanic's user avatar
1 vote

Does entanglement allow enhanced communication efficiency?

In your argument, you are missing the relativistic causality. Bob and Alice simply cannot decide who did the measurement first because their space-time measurement events are connected by the space-...
hbadger19042's user avatar

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