33
votes
Accepted
What is quantum gate teleportation?
Quantum gate teleportation is the act of being able to apply a quantum gate on the unknown state while it is being teleported. This is one of the ways in which measurement-based computation can be ...
- 52.3k
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 ...
- 2,522
10
votes
What is quantum gate teleportation?
Gate teleportation is in principle a method that allows the creation of different gates from an available set of gates, by teleporting qubits through entangled states. An example of the use of this ...
9
votes
Accepted
How is quantum teleportation generalized to qudits?
Let's define the shift and clock matrices (the generalisation of the Pauli X and Z matrices) as
$$
X=\sum_{i=0}^{d-1}|i+1\text{ mod }d\rangle\langle i|\qquad Z=\sum_{i=0}^{d-1}\omega^i|i\rangle\langle ...
- 52.3k
9
votes
Accepted
Trying to build a circuit for quantum teleportation on IBMQ I get ERROR_RUNNING_JOB error
The issue is that you are applying operations after measurement gates and this is currently not available on the real hardware. I think the hardware also does not support reset operations mid-way ...
- 3,213
8
votes
Accepted
Why is super-dense coding called the inverse of quantum teleportation?
In quantum teleportation, one starts with an entangled state shared between two parties, and (after some messing at the sender's side), two classical bits are transmitted from one party to the other ...
- 52.3k
8
votes
Using a fractional number of classical bits within quantum teleportation
I don't know for sure how you would achieve fewer than two bits of classical communication for a teleportation, but here's one way that you could have a non-integer number: if you teleport a qudit ...
- 52.3k
8
votes
Accepted
Can $2^n$ bits be sent with $n$ instances of quantum teleportation?
Quantum teleportation can send a single qubit from Alice to Bob, with two classical bits
Correct, on the condition that Alice and Bob also have an entangled qubit pair shared between them. This ...
- 1,235
7
votes
Accepted
When you act on a multi-qubit system with a 2-qubit gate, what happens to the third qubit?
Whenever you have a quantum gate (like a CNOT) acting on some qubits but not others, it is assumed that the other qubits are acted on with the identity operator. This is done using the "Left Kronecker ...
- 12.8k
7
votes
Accepted
Quantum teleportation: second classical bit for removing entanglement?
Your initial calculations are correct. When Alice performs her first measurement and gets a 0 outcome then, as you say, Alice and Bob are left sharing a two-qubit state
$$
|\Psi\rangle=\alpha|00\...
- 52.3k
7
votes
What happens to the Bell state qubits after the Quantum Teleportation?
They get measured as part of the teleportation. It doesn't matter what happens to them after that. You can throw them away, reset them back to $|0\rangle$ and re-use them for something else, whatever.
- 30.1k
7
votes
Accepted
how to prove quantum teleportation can't be achieved by sending only one classical bit
Alice sent 1 bit to Bob.
But that bit contained 1 qubit (via too good teleportation).
But that qubit contained 2 bits (via superdense coding).
But those 2 bits contained 2 qubits (too good ...
- 30.1k
6
votes
Accepted
Understanding this description of teleportation
The first two qubits stay on the sender's side, and since they are not entangled with the receiver's qubit, it's not necessary to mention them any further — we switched to discussing the receiver's ...
- 8,296
6
votes
Compute the output of the quantum teleportation circuit
Since your circuit is teleportation, $|C\rangle =|\varphi\rangle$ and since you measured $|11\rangle$ on $|AB\rangle$ the answer is $|ABC\rangle = |11\rangle|\varphi\rangle$.
Now, let look why this ...
- 13.1k
6
votes
Accepted
Generalising the standard quantum teleportation protocol: what are the possible unitaries?
A necessary and sufficient condition on the unitary $B$ is that its columns all correspond to maximally entangled states.
There also does not need to be any relationship between the two unitaries ...
- 4,958
6
votes
Why can’t I use quantum teleportation to transmit data FTL 1/4 of the time?
Suppose Alice wants to send Bob a 1000 bit message. To receive the message, Bob flips 1000 coins and writes down the results as 0s and 1s. About 50% of the random bits in the message that Bob ...
- 30.1k
6
votes
Is it possible to have Quantum Teleportation Protocol without using classical channel?
This "protocol" is completely wrong. The author is simply preparing the state $|\psi\rangle$ on Bob's side and leaving it there untouched. Meanwhile, Alice prepares a maximally entangled ...
- 2,258
5
votes
Accepted
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 ...
- 1,725
5
votes
Accepted
Generalization for $n$ quantum teleportations
The simplest way to generalize teleportation is to just repeat it. If you have one EPR pair divided between Alice and Bob, teleportation allows you to move one qubit from Alice to Bob (or vice versa) ...
- 30.1k
5
votes
Using a fractional number of classical bits within quantum teleportation
I recently found a paper by Subhash Kak that introduces teleportation protocols that require lesser classical communication cost (with more quantum resource). I thought it'd be better to write a ...
- 361
5
votes
What is the maximum separation between two entangled qubits that has been achieved experimentally?
I believe the current record is held by the Jian-Wei Pan group in China, who are able to generate entanglement via a satellite. The journal article is here, while there's plenty of media coverage that ...
- 52.3k
5
votes
Accepted
Quantum teleportation of a state, from one of two bases
Alice receives a quantum state $|\psi\rangle$, which is an element of some basis $\mathcal{B}$, though she does not know what $\mathcal B$ is. She then teleports this to Bob, who is told by someone ...
- 11.6k
5
votes
In what ways can qubits be used for applications that do not require entanglement?
One (obvious) application is the generation as True Random Number Generators,
e.g. IDQ, or you can download some here Free True Random Numbers (please do not use these for security relevant ...
- 364
5
votes
Accepted
Understanding quantum teleportation algorithm from qiskit tutorials
Your circuit does not measure $q_2$ qubit after teleportation; I guess that is why teleportation of $|1\rangle$ qubit is shown incorrectly.
- 3,174
5
votes
Accepted
Does principle of deferred measurement imply information can travel faster than light?
I think faster than light communication is more stubborn than that :-)
The principle of deferred measurement, to quote Nielsen and Chuang, page 186, is
Measurements can always be moved from an ...
- 8,296
5
votes
Accepted
Quantum teleportation of a mixed state through a pure state?
The teleportation should behave just the same with a mixed state as it does with a pure state. I'm going to assume a bit of familiarity with how teleportation works for pure states, as you can find ...
- 5,715
5
votes
Is there some nice physical intuition to get for quantum teleportation
In a certain sense, local measurements of entangled states already can be viewed as a kind of "teleportation".
For example, suppose Alice and Bob share the Bell state $B=\frac{1}{\sqrt{2}}(|...
- 6,443
5
votes
Accepted
What is the name of this "ancilla based" process to implement gates
This is the circuit on which the magic state model is based. As they say in the linked paper, such a circuit is often called a gadget, more specifically a state injection gadget.
The reason why such ...
- 4,157
5
votes
Is quantum teleportation fully secure (in principle)?
Yes, in the ideal case it is perfectly secure, the probabilities of each outcome in the measurement in the Bell basis are 1/4 independently of the input state.
Indeed it does. For example, suppose ...
- 2,258
5
votes
Accepted
Is quantum teleportation fully secure (in principle)?
Adding to Mateus Araújo's answer:
An easy way to see that the classical bits are uncorrelated with the message in the idealized protocol is that any correlation would amount to a measurement of the ...
- 788
Only top scored, non community-wiki answers of a minimum length are eligible