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1500 questions
6
votes
3 answers
How do we physically initialize qubits in a Quantum register?
In quantum algorithms we need to initialize the qubits at the start of our algorithm in some quantum register. Suppose that if we are working with a four qubit quantum register we can initialize the register into values such as $|0000\rangle$ or…
K Sarkar
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6
votes
2 answers
Randomness from deterministic machine
It is known that in a classical computer we can't generate a purely random number by deterministic process. I am taking a course in Quantum Computing, recently I learnt that using state we can generate a deterministic process which will produce…
tarit goswami
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6
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How scalable are quantum computers when measurement operations are considered?
From a high-level point of view, given a quantum program, typically the last few operations are measurements.
In most cases, in order to extract a useful answer, it is necessary to run multiple times to reach a point where it is possible to…
Juan Leni
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6
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2 answers
Symmetry in Conditional Phase Shift Gates and Realizing CNOT through HCZH
Why are conditional phase shift gates, such as CZ, symmetrical? Why do both the control and target qubit pick up a phase?
Furthermore, assuming that they are symmetrical, when using a CNOT gate as an H gate on the target qubit, a CZ gate, and…
Eric Li
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6
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1 answer
Classical XOR gate in Quantum Circuit
Can we use classical XOR gate in a quantum circuit? Or are there any alternatives for XOR gate?
Govind
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6
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0 answers
Photon Entanglement using SPDC
Are there any good references where from I can learn about photon entanglement using spontaneous parametric down-conversion (SPDC)?
Govind
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6
votes
2 answers
How do we derive the density operator of a subsystem?
The density operator can be used to represent uncertainty of quantum state from some perspective, aka a subsystem of the full quantum system. For example, given a Bell state:
$|\psi\rangle = \frac{|00\rangle + |11\rangle}{\sqrt{2}}$
where Alice has…
ahelwer
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6
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1 answer
Transmons and cooper pair box qubits: two islands or a single island and a reservoir
In scientific literature, one typically describes Cooper pair boxes as a small superconducting island coupled to a superconducting reservoir (say, a large ground plane of superconducting metal, or a large piece in any case) via a Josephson junction.…
user129412
- 170
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6
votes
3 answers
Example of Hamiltonian Simulation solving interesting problem?
Hamiltionian Simulation (= simulation of quantum mechanical systems) is claimed to be one of the most promising applications of a quantum computer in the future.
One of the earliest – and most important – applications of a quantum
computer is…
JanVdA
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6
votes
4 answers
How to re-create the following circuit image?
What would be the best way to re-create the following image of the HHL quantum circuit without compromising on image quality (the image is from this review paper)?
Using qasm2circ I can create the basic circuit. But I don't know any good…
Sanchayan Dutta
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6
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1 answer
Can we process infinite matrices with a quantum computer?
Can we process infinite matrices with a quantum computer?
If then, how can we do that?
KYHSGeekCode
- 171
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6
votes
2 answers
What exactly are "quantum rotors"?
The Wikipedia entry on the subject is rather short. I am also curious about generalizations of quantum rotors in n-dimensions. An introductory explanation with at least one resource for further reading would be greatly appreciated.
user820789
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6
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2 answers
Are quantum simulators like Microsoft Q# actually using quantum mechanics in their chips?
Unlike Google's Bristlecone or IBM's Qbit computer, do simulators like Q# or Alibaba really use quantum mechanics anywhere in their physical chips? Are they just defining properties using a classical computer and trying to achieve quantum…
Yashank
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6
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1 answer
Does the need of many quantum algorithms to be repeated several times impair the efficiency gains?
As I understand so far, in some algorithms such as Simon's algorithm, swap-test algorithm or quantum k-means algorithm, we repetitively perform a measurement yielding a classical result. Consequently, this pushes us to run the whole algorithm again…
Aman
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6
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2 answers
Just want to confirm: Do two CNOT gates cancel each other?
I see somewhere that this happens:
But I wonder if this is just identity.
Ka Wa Yip
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