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Continued Fraction Algorithm in Shor's Algorithm

I am just trying to make the final link of Shor's algorithm clear. Here $r$ is the order of $x$ modulo $N$. We have a number $\psi$, which for a rational number $\dfrac{s}{r}$ satisfies ...
0
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0answers
36 views

What devices are necessary to do quantum computing experiments? [closed]

I'm trying to get a sense of what quantum computing is. I've picked up a few books, but none of them - so far - actually describes HOW quantum computing experiments are conducted. Specifically I'm ...
2
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0answers
35 views

In Grover and Shor Algorithms 2 registers of qubits are handled at books, but it's really just one seen as 2?

I found in the literature that we require at least two quantum registers for arithmetics operation. Example: The function $f(x)=x^2$ is then a unitary evolution of the two registers, in this ...
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1answer
44 views

Quantum computer simulators [closed]

What are good, free, open source, GUI-based quantum computer simulators? I remember there used to be a Java-based one that was very good, but it doesn't seem to be online anymore, or it's relocated.
0
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1answer
23 views

Condition for quantum error correction based on encoded states

I am trying to understand the properties of quantum error correcting codes. Consider a quantum code on a lattice, with the property that a given region $R$ is correctable (for any error localized to ...
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0answers
49 views

Quantum Error Correction: Surface code vs. color code

Recently, two groups working on quantum computers published results on quantum error correction. The first was Rainer Blatt's group, who used trapped ions to perform a topologically encoded qubit ...
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0answers
18 views

Have there been any experiments that have demonstrated a quantum error correcting code?

Has quantum error correction been demonstrated? I know that classical error correction has been demonstrated by [1], they correct a single bit flip error, but has anyone been able to detect and ...
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0answers
37 views

Properties of controlled z-rotations

Given n qubit gate of the form c-z-z-z... (shorthand for c-z between qubit 1 and 2 followed by c-z between 1 and 3 and so on up to n qubits) it seems to be possible to find local unitaries which will ...
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0answers
61 views

QFT Perturbative analysis of multiple atom-level quantum computers close to each other

Following up on this question, I'm wondering about electromagnetic interactions perturbation expansions close to a "black-box" quantum computer and modularity of Feynman diagrams in general. Let me ...
3
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0answers
50 views

How would a quantum computer receive input from a classical computer?

One of the potential applications of a quantum computer would be as a coprocessor to a classical computing system, much in the same way as a graphics processing unit (GPU) performs specialized ...
2
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3answers
157 views

Can existing quantum computers be considered evidence for parallel universes?

In this video ( http://www.youtube.com/watch?v=bJpIclDmi2M ) Max Tegmark , a MIT cosmologist says that if we build a quantum computing successfully it will be a evidence that Parallel Universes ...
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0answers
38 views

Conjugate of unknown qubit?

I have seen this problem somewhere on stack exchange, but I have a separate question. Given a qubit which is unknown say $\alpha|0\rangle +\beta|1\rangle $ ( $\alpha, \beta$ are unknown ) is there a ...
2
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2answers
131 views

What is the difference between a bit and a qubit?

I am Computer Science student and learning about quantum computing. But, I have a problem in understanding Bit and Qubit relationship. A bit with 2 bits = 4 states 00,01,10,11--- 1 state at a time. ...
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0answers
34 views

How does one devise a Grover quantum oracle despite the no-cloning theorem?

I think I have misunderstood Grover's quantum search algorithm, and would appreciate clarification. From what I understand, the Oracle operator takes an index register of qubits $|x\rangle$ (that ...
3
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1answer
74 views

Deutsch's Algorithm. Unitary Transform $U_f$

I'm studying Deutsch's algorithm and I keep coming across the phrase along the lines of "There is a unitary transform (a sequence of quantum gates) $U_f$ that transforms the state $|x\rangle |y\rangle ...
2
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1answer
74 views

Would quantum computers be better at everything a GPU normally does? [closed]

I have a very basic understanding of what GPU's and quantum computers are good at. To me, it seems like they overlap, but maybe this isn't completely true. GPU's are good for graphics which requires a ...
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1answer
41 views

Is the process on initialization of qubits unitary?

It is said in some texts, that quantum computer undergoes only 2 types of transofrmations: 1) unitary evolution while computing and 2) non-unitary transformation ...
1
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1answer
30 views

Why are crystals so useful for quantum isolation?

Some implementations of quantum gates (in the hopes of building a quantum computer one day) use crystals to isolate the qubits (to prevent decoherence). Why is a crystal so much better than an ...
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1answer
214 views

The fine structure constant - can it genuinely be a random variable?

The question Does it make sense, and are there physical reasons to think about the fine structure constant as a (very concentrated) probability distribution rather than a single real number? ...
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1answer
49 views

What is trivial and non-trivial gate in computing?

My question seems like it should be posted in Computer Engineering section, but below is how I found this word. I was reading the textbook: Quantum Computation And Quantum Information - by Michael A. ...
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2answers
210 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 ...
0
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1answer
56 views

Why quantum computer is so fast factoring numbers?

I am trying to get myself a more clear understanding of the root of significant acceleration in number factoring by P. Shor's algorithm. I am probably missing something but q-bits for me are no more ...
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2answers
104 views

Will Quantum Computation fail if spacetime is discrete?

Will Quantum Computation fail if spacetime is discrete? Basically, would a discrete spacetime impose unexpected limits on how many Qubits could be used in calculations? Conversely, can quantum ...
0
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1answer
101 views

Are there any known physical implementations of quantum gates?

I was wondering if there are any known implementations of a small number of quantum gates that can interact with each other. Certainly we don't have a "complete" set of quantum gates (where ...
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0answers
48 views

What is the output of a quantum simulator?

First off the bat, the context of this question is philosophical, but please don't run away, since a physicist is required to comment on this one: Philosophers sometimes contemplate a hypothetical ...
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1answer
105 views

What does it mean that quantum teleportation can be classically simulated?

Quoting here from Quantum Computation by Neilsen and Chuang : (Gottesman–Knill theorem) Suppose a quantum computation is performed which involves only the following elements: state preparations ...
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25 views

Realisation of arbitrary controlled quantum gate

I am interested if there's some known approach when constructing quantum gates out of universal set. I was trying to construct Controlled Z gate (gate that will apply pauli-Z gate on the target qbit ...
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1answer
55 views

What are the “other” Hadamard matrices?

The Pauli matrices $$ X = \begin{pmatrix}0&1\\1&0\end{pmatrix}, Y=\begin{pmatrix}0&-i\\i &0\end{pmatrix},\,\text{and}\, Z=\begin{pmatrix}1&0\\0&-1\end{pmatrix} $$ can be used ...
2
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1answer
83 views

Bell State vs. Bell Measurement

What is the difference between a Bell state and a Bell measurement? I am studying quantum computation, and Bell states have been introduced. I understand that Bell states can be prepared using the ...
2
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0answers
25 views

Information retrieval from a database

Consider a database $\cal D$ containing $N$ entries $A_0, A_1, ... A_{N-1}$, which are some fixed and unknown strings of $k$ bits; you can access this database sending a coherent superposition of ...
0
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1answer
86 views

What is a good book for quantum mechanics and quantum computation? [duplicate]

I am looking for a book in quantum computers for self-learning.The kind of book that teaches quantum-mechanics + quantum-computation. I have basic understanding in calculus , linear-algebra (like ...
4
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2answers
73 views

Tensors of rotations about an arbitrary vector in C^2

I'm trying to solve the following equation: $$e^{-i\theta/2 \sigma_{\vec{i}}^A} \otimes e^{-i\theta/2 \sigma_{\vec{i}}^B} |\Psi\rangle_{AB} = e^{i\phi} |\Psi\rangle_{AB} $$ where $e^{i\phi}$ should ...
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3answers
235 views

A question on quantum computing and de Broglie's pilot wave theory

I don't know much about quantum computing except what I have read about on wiki and popsci. I have been reading about the de Broglie-Bohm pilot wave theory and how they describe quantum mechanics in ...
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0answers
20 views

A question on quantum computing? [duplicate]

I dont know much about quantum computing except what i have read about on wiki and popsci. I have been reading about the de broglie-bohm pilot wave theory and how they describe quantum mechanics in ...
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0answers
119 views

Eigenvalue of the adiabatic Hamiltonian of Farhi's three qubit 2-SAT problem

I was trying to reproduce example 3.3 of Quantum Computation by Adiabatic Evolution by Edward Farhi et. al. This is an adiabatic algorithm to solve an instance of three qubits 2-SAT problem. I think ...
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0answers
71 views

What math do I want to focus on for 1) quantum computing and 2) quantum physics? [closed]

What math do I want to focus on for 1) quantum computing and 2) quantum physics? I am interested in studying quantum computing and the Higgs Boson (quantum physics?) and ultimately working in some ...
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3answers
144 views

Scalable quantum computation vs Uncertainty Principle

tl;dr. : If we want the result of a quantum computation to have scalable more bits, we will need inner measurements to have scalable precision, if we already know the result of the computation (from a ...
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2answers
89 views

Quantum computing and ambiguity

I do a bit of hobby programming and I often search the internet for little oddities that are fun to ponder over. I have read a few passages that try to explain quantum computing to the layman like ...
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1answer
53 views

Is the subadditivity of quantum entropy valid in the infinite-dimensional case?

Does the subadditivity (and strong subadditivity) of quantum entropy hold for infinite dimensional quantum systems as well? Unfortunately the books in my hand give proof for finite dimensional cases ...
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0answers
161 views

Output of a beamsplitter with photon number (Fock) state inputs

Given a beamsplitter drawn below, where $\hat{a}$ and $\hat{b}$ are input modal annihilation operators, transmissivity is $\tau\in[0,1]$, and output modal annihilation operators are ...
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1answer
66 views

About Shor's error correcting algorithm

In this paper, http://arxiv.org/abs/1301.4504 in equation 4.1 in what sense are the two states a "9-qubit state"? I did not understand this counting. Can someone explain what are the different $X_i$ ...
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0answers
98 views

Nature as a calculator [closed]

I wondered whether physical experiments can find the outcome of otherwise intractable mathematical problems. For example, solitons or other non-perturbative effects in QFT cannot be seen at any ...
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0answers
69 views

About the Hayden-Preskill circuit

Can someone summarize as to what are the problems and/or the open questions with the Hayden-Preskill circuit? (in the context of understanding black-holes or as a computer science question)It gives a ...
3
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0answers
32 views

Different forms of the Adiabatic Theorem

I've been reading several papers on Adiabatic Quantum Computation, and I am confused by the form in which the adiabatic approximation condition is presented. For example (quant-ph/0001106 eq 2.8) ...
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1answer
88 views

What is Getting in the Way of Testing D-Wave?

I know there are other questions i.e. Do quantum computers manufactured by D-Wave Systems, Inc. work? , What can the D-Wave quantum computer do? , etc. But I can't seem to find my answer. What is ...
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1answer
49 views

Partial measurement (destructive) collapses |1> to |0>

In the following QScript program: ...
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0answers
172 views

Is it possible to construct a quantum “computer” using laser light similar to the double-slit experiment?

Is it possible to construct an arrangement of optical devices (lasers, mirrors, slits, splitters) such that the construction could carry out a single quantum "computation"? I understand that such a ...
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3answers
185 views

Does processing for a quantum computer take place in other universes?

Apologies in advance if my question seems misinformed. I am a software developer, and neither quantum mechanics nor physics are my specialties. From ...
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0answers
64 views

Can the new results (about photonic time travel) make quantum computers feasible?

New results published about photonic time travel, reference here make quantum computers a reality in the near future? These results seem to indicate that there can be qubits that can exhibit nonlinear ...
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69 views

Subgroups of the Clifford Group

We recall the definition of a Clifford group (over $n$ qubits) is the set of unitary transformations: $$\{U: UPU^\dagger\in\mathcal{P}\}$$ where $\mathcal{P}$ denotes the corresponding Pauli group ...