All Questions
43 questions
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1
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Is two degree quantum entanglement possible? And by two degree of entanglement I mean one in space and other in time? [closed]
Whenever we try to entangle two particles, the entanglement lasts for a very short period. If we observe our present universe we can see that all the matters present in our universe are finely ...
-2
votes
1
answer
148
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What is meant by " a basis is diagonal"?
I am trying to understand Schmidt decomposition. I am stuck in one sentence here. See the example picture.
Here, I can understand everything except the line "For both
HA and HB the Schmidt basis ...
1
vote
0
answers
258
views
Does the required cooling energy increase when Quantum computer processors with more and more entangled Qubits are produced?
IBM has succeeded in 2021 in realizing a Quantum computer with 127 entangled Qubits (Processor Eagle). A Quantum computer with 433 entangled Qubits (Processor Osprey) was planned for 2022, and a ...
- 53
1
vote
5
answers
2k
views
Mathematical explanation of bra-ket notation in quantum mechanics
$\newcommand{\hp}[1]{\hphantom{#1}}$
We have the entangled state of two pairs of qubits:
$$
|\psi \rangle =\frac{1}{2}|0011\rangle-\frac{1}{2}|0110\rangle-\frac{1}{2}|1001\rangle+\frac{1}{2}|1100\...
- 253
0
votes
3
answers
845
views
Role of entanglement in quantum computing
I'm not a physicist and thus, I'm looking for a simple explanation on the role of entanglement in making quantum computers fast. I got a good analogy of a qubit: a coin tossed in the air can be ...
- 1
1
vote
0
answers
173
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What exactly is meant by the quality of a qubit?
When looking at a quantum annealer, we can see that D-Wave solutions have produced an annealer with over 5000 qubits whilst other companies that take a quantum gate approach have only managed 127 (IBM)...
- 988
-1
votes
1
answer
151
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How does CNOT gate work?
In Quantum Computation there is (among others) a so called CNOT gate. Its control input |x> is "driven through", while the other input |y> is converted to some other state, depending ...
- 1,391
0
votes
1
answer
63
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Displacement gate on an arbitrary quantum state
I am reading this reference. In this article, the author define the Heisenberg-Weyl operators (Eqs. [148] in the reference):
$$X(s)=e^{-is\hat{p}/2} \tag{1},$$
$$Z(t)=e^{it\hat{q}/2} \tag{2},$$
where $...
2
votes
0
answers
139
views
Why does the no-cloning theorem imply the monogamy of entanglement?
I have seen papers where they mentioned that the monogamy of entanglement can be seen as a consequence of the no-cloning theorem. Could somebody sketch this out?
N.B.: I have seen the argument that ...
- 1,471
1
vote
0
answers
44
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What entanglement measures are known to satisfy entanglement monogamy?
As the title says, what entanglement measures are known to satisfy the entanglement monogamy principle?
Im specially interested in those entanglement measures that apply to mixed states.
- 1,471
3
votes
2
answers
121
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Why does entanglement negativity not satisfy the triangle inequality in the usual sense?
I am a bit puzzled, I’ve read in some places, like the original paper by Vidal, that
$$
\mathcal{N}(\sum_n a_n \rho_n)\leq \sum_n a_n \mathcal{N}(\rho_n)
$$
whenever $a_n \geq 0$ and $\sum_n a_n =1$. ...
- 1,471
3
votes
0
answers
116
views
How does this quantum circuit work? [closed]
I am getting a bit confused about how to trace through a quantum circuit.
So, for example, if you have the circuit below:
I know that the first gate would split an arbitrary state alpha|0> + beta|...
- 39
0
votes
0
answers
111
views
What gate combinations create entangled two-qubit states?
I know that in order to make a two qubit entangled state, this quantum circuit is used:
But I was wondering if there are any other gate combinations which also create entangled two quit states.
If ...
- 21
3
votes
1
answer
443
views
How can we "isolate" a qubit
From Wikipedia : In ion quantum computer, if the ions are not properly isolated, noise can result from ions interacting with external electromagnetic fields, which creates random movement and destroys ...
- 49
1
vote
1
answer
199
views
Confusion regarding bra-ket notation and proof of a ket equation
My question is two-part. First, imagine a bipartite quantum state $|\Phi \rangle_{AB}$, made of $2n$-qubits, shared between Alice and Bob (with $n$-qubits each). Alice performs some unitary operation $...
- 777
3
votes
1
answer
512
views
Applying a rotation on an entangled state
I want to understand an experiment but I am struggling with the (basic) math/braket notation.
In the experiment two ions are entangled and separated into two wells $A$ and $B$. The spin state of the ...
2
votes
1
answer
272
views
How Do I Calculate the Score of a Bell's Game
I am reading "Quantum Chance" by Nicolas Gisin. I would like to know how to calculate the Bell Game outcome given in the following section of the book.
BACKGROUND
The Bell Game begins with a pair ...
1
vote
0
answers
193
views
What is the definition of genuine entanglement?
I can't seem to find a definition for genuine entanglement but it is being used in an article I'm reading and the references inside but I'm unable to find the precise definition.
One thing I was able ...
1
vote
0
answers
89
views
Can a quantum computing advantage exist in a deterministic universe?
Is a deterministic universe with nonlocal hidden variables incompatible with the quantum superpositioning of states that is required for quantum computing?
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-2
votes
1
answer
404
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Is quantum entanglement contradictory with Schrödinger's cat?
As I understand, an electron spin is in a superposition state until the spin is observed. Due to the observation, it will either be spin up or spin down.
Due to quantum entanglement, if one electron ...
- 29
0
votes
1
answer
49
views
What distinguish a non-interacting two fermions gate from an interacting one?
We start with a Hilbert space consists of two fermions(a and b), which is 4-dimensional. The basis would be $|vec>$,$b^\dagger|vac>$,$a^\dagger|vac>$,$a^\dagger b^\dagger |vac>$.
Denote ...
- 171
1
vote
0
answers
76
views
What is the simplest circuit on a quantum computer that "proves" superposition/entanglement
I am a Physics Teacher at pre university level.
Tunneling, wavefunctions and uncertainty are on the syllabus on a very vague way. Quantum superposition and entanglement are not but tie in well and I ...
1
vote
0
answers
50
views
5 qubit quantum error correction property [closed]
Having
$$\eqalign{
|v_0⟩&=|00000⟩+|11000⟩+|01100⟩+|00110⟩+ {}\cr
&\quad |00011⟩+|10001⟩−|10010⟩-|10100⟩− {}\cr
&\quad |01001⟩−|01010⟩−|00101⟩−|11110⟩− {}\cr
&\quad |...
- 11
3
votes
1
answer
670
views
How to identify whether a quantum state is entangled or separable if you can measure it only in one basis?
Suppose you have two qubits and don't know whether they're in an entangled state $ \frac{1}{\sqrt{2}}\left(|0,0\rangle + |1,1\rangle\right)$ or in an equal mixture of states $ |0,0\rangle $ and $ |1,1\...
- 362
0
votes
0
answers
28
views
How do I apply no signaling condition for the given Quantum Adder problem
The Unitary transformation for the Imperfect Quantum Adder problem is such:
Both the states belong to two Hilbert Spaces and we are trying to add both states to one system using Ancillary qubit.
I ...
0
votes
0
answers
57
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Intuition behind quantum CNOT gate applied to a pair of electrons [duplicate]
I'm looking for some intuition behind how a cNOT gate works. I think I understand the mathematics; but, I'm having trouble imagining how two electrons would interact to produce the predicted result.
...
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-3
votes
2
answers
205
views
Do qubits need to be in superposition to be entangled? [closed]
Do qubits need to be in superposition to be entangled?
Put another way, can qubits be entangled but not in superposition?
3
votes
0
answers
470
views
Are there any physical realizations of a rebit (a qubit with real coefficients for probability amplitudes of a two-state system)?
While being introduced to the world of quantum computation and qubits, I’ve come across the term rebit, which I understand to mean a two-state quantum system that may be expressed as a real linear ...
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3
votes
1
answer
794
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quantum superdense coding -How many qubits are needed?
This is an extract from Wikipedia about superdense coding:
"In quantum information theory, superdense coding is a quantum communication protocol to transmit two classical bits of information (i.e., ...
- 149
0
votes
1
answer
169
views
Is a GPU accelerated Quantum computer simulator publishable research?
I have built a GPU accelerated quantum computer simulator that is quicker then libquantum and the IBM QISkit simumators. Is the work done on this (methods, archetecture) publishable?
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0
votes
1
answer
63
views
Physical system for exchanging entanglement between types of particles
What is an example of physical system in which entanglement is transferred from one pair of particles to a different pair of a completely different type of particle?
For instance, if I have two ...
- 781
-3
votes
1
answer
136
views
Is every Quantum Computer working with entangled particles? [closed]
Is every Quantum Computer working with entangled particles?
I ask this question, because entangled particles are not allways local.
I read that a Quantum Gate can be used to concatenate quantum ...
2
votes
0
answers
317
views
About complexity of quantum states
From quantum computation point of view, the complexity of a quantum state $|\psi\rangle$ can be defined as the the complexity of the quantum circuit that can generate the state $|\psi\rangle$ from an ...
- 1,576
0
votes
2
answers
450
views
Measuring a certain qubit in a three qubit system
Assuming I have a state $|\psi\rangle$ that is a superposition of 3 qubits ($|ijk\rangle\ \ \ \ i,j,k\in\{0,1\}$). When it is said that we measure only the first qubit in, say, the y-axis, does that ...
- 135
-2
votes
2
answers
142
views
Can a non-entangled qubit be teleported by entangling it?
Let's say I have a qubit that is not entangled in state $\psi$. I want to teleport this qubit by entangling it with another qubit but still getting $\psi$ back in the end.
Is this possible, or would ...
- 497
2
votes
1
answer
201
views
Quantum teleportation of atomic states that involve energy [duplicate]
With quantum computing the concern is with information, and when quantum teleportation appears, the states being transferred are often spin states.
However, there is an energy difference, even if ...
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2
votes
2
answers
8k
views
What's the Cause of Quantum Entanglement? [duplicate]
What is the cause of quantum entanglement?
When two particles become entangled what property of them basically changes as to establish a link between them and how the information is exchanged between ...
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13
votes
1
answer
872
views
Quantum computing records (entangled qubits)
What is the current record number of entagled qubits and how has this number been increased?
The latest result on stack exchange, which is 3 years old, reports 14 via
this post: How many stabilised ...
- 722
9
votes
2
answers
2k
views
Is entanglement necessary for quantum computation?
Is entanglement necessary for quantum computation?
If there was no error in the computation,superposition of states would be sufficient for quantum computation to be carried out.Is this right?
6
votes
1
answer
2k
views
Can we measure two entangled qubits in two different bases simultaneously?
Suppose we have the pair of entangled qubits:
$$ |\psi\rangle = \frac{1}{ \sqrt{2} } ( |00\rangle + |11\rangle ),$$
where $|\psi\rangle$ is one of the $4$ Bell states.
Suppose now that we give one ...
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6
votes
1
answer
4k
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Why do we want to entangle qubits?
The title is pretty much all I want to ask. Why are qubits entangled? To my knowledge (which isn't that deep) a quantum register can be realized without entangling the qubits.
- 263
9
votes
2
answers
1k
views
Quantum Computing, Qubit Creation/Entanglement
I am currently a high school student researching quantum computing. I was referred to this site by Google and a friend. Currently I am researching the qubit part of quantum computing. My question is ...
12
votes
2
answers
2k
views
What is quantum discord?
What is quantum discord? I stumbled upon this term on Quantum Computing: The power of discord, but have never heard of it before. Can you give a bit more mathematical explanation of the term here?
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