Questions tagged [quantum-computing]
Quantum computation and computational issues related to quantum mechanics
42
questions
22
votes
1answer
812 views
How much computational power fits into a cubic centimeter?
This question is a followup on the question about DNA algorithms asked by Aadita Mehra.
In comments there, Joe Fitzsimmons said, in part:
[T]he radius of the system must scale proportionately to ...
42
votes
16answers
4k views
Physics results in TCS?
It seems clear that a number of subfields of theoretical computer science have been significantly impacted by results from theoretical physics. Two examples of this are
Quantum computation
...
15
votes
6answers
7k views
Quantum computing project ideas
I'm undergraduate computer science student and I'm currently planning for my graduation project. I need some ideas in quantum computing field. any help?
27
votes
2answers
2k views
NP-intermediate problems with efficient quantum solutions
Peter Shor showed that two of the most important NP-intermediate problems, factoring and the discrete log problem, are in BQP. In contrast, the best known quantum algorithm for SAT (Grover's search) ...
16
votes
1answer
787 views
Reading up on $BQP = BPP^{BQNC}$
What should I read to understand this problem?
The power of small-depth quantum
circuits. Is $BQP = BPP^{BQNC}$? In other
words, can the "quantum" part of any
quantum algorithm be compressed ...
32
votes
11answers
2k views
What is the quantum computational model?
I have occasionally heard people talk about quantum algorithms and about states and the ability to consider multiple possibilities at once, but I have never managed to get someone to explain the ...
15
votes
2answers
939 views
Quantum analogues of SPACE complexity classes
We often consider complexity classes where we are bounded in the amount of space our Turing machine can use, for example: $\textbf{DSPACE}(f(n))$ or $\textbf{NSPACE}(f(n))$. It seems that early in ...
10
votes
4answers
669 views
Bounding the gap between quantum and deterministic query complexity
Although exponential separations between bounded-error quantum query complexity ($Q(f)$) and deterministic query complexity ($D(f)$) or bounded-error randomized query complexity ($R(f)$) are known, ...
10
votes
1answer
595 views
What is the proof that quantum computers can efficiently simulate arbitrary quantum mechanical systems?
JBV suggested I turn some comments into a question, so here goes.
Another question [1] asks about applications of QM computing. One answer [2] was "efficiently simulating quantum mechanics". ...
5
votes
0answers
607 views
Learning quantum CS [duplicate]
Possible Duplicate:
What is the quantum computational model?
What is the best way to study quantum branch of CS for the person with rather advanced background in classical CS? Does one need to ...
81
votes
2answers
10k views
Was the reduction in Shor's algorithm originally discovered by Shor?
This is a "historical question" more than it is a research question, but was the classical reduction to order-finding in Shor's algorithm for factorization initially discovered by Peter Shor, or was ...
19
votes
7answers
26k views
Universities for Quantum Computing / Information?
Which universities have a strong quantum computing curriculum, and offer some type of quantum computing/information courses/research?
The aim here is to collect a useful list for someone considering ...
20
votes
4answers
5k views
Is there any connection between the diamond norm and the distance of the associated states?
In quantum information theory, the distance between two quantum channels is often measured using the diamond norm. There are also a number of ways to measure distance between two quantum states, such ...
20
votes
1answer
645 views
Consequences of $BQP \subseteq P/poly$?
While Adleman's theorem shows, that $\mathsf{BPP} \subseteq \mathsf{P}/\text{poly}$, I'm not aware of any literature investigating the possible inclusion of $\mathsf{BQP} \subseteq \mathsf{P}/\text{...
20
votes
4answers
707 views
Is there an equivalent to derandomization for quantum algorithms?
With some randomized algorithms you can derandomize the algorithm, removing (at a possible cost in run time) the use of random bits and maximizing some lower bound on the objective (usually computed ...
17
votes
5answers
3k views
Real world applications of quantum computing (except for security)
Let's assume that we have built an universal quantum computer.
Except for security-related issues (cryptography, privacy, ...) which current real world problems can benefit from using it?
I am ...
51
votes
3answers
2k views
Rigorous security proof for Wiesner's quantum money?
In his celebrated paper "Conjugate Coding" (written around 1970), Stephen Wiesner proposed a scheme for quantum money that is unconditionally impossible to counterfeit, assuming that the issuing bank ...
27
votes
5answers
876 views
Quantum proofs of classical theorems
I'm interested in examples of problems where a theorem which seemingly has nothing to do with quantum mechanics/information (e.g. states something about purely classical objects) can nevertheless be ...
20
votes
2answers
934 views
$\ell_p$-norm preserving Turing machines
Reading some recent threads on quantum computing (here,here, and here), make me remember an interesting question about the power of some kind of $\ell_p$-norm preserving machine.
For people working ...
19
votes
1answer
897 views
Why does Odlyzko improvement of Shor's Algorithm reduces the number of trials to $O(1)$
In his 1995 paper Polynomial-Time Algorithms for Prime Factorization and Discrete Logarithms on a Quantum Computer, Peter W. Shor discusses an improvement on the order-finding part of his ...
14
votes
1answer
742 views
What is known about multi-prover interactive proofs with short messages?
Beigi, Shor and Watrous have a very nice paper on the power of quantum interactive proofs with short messages. They consider three variants of 'short messages', and the specific one I care about is ...
9
votes
2answers
825 views
Is adiabatic quantum computing as powerful as the circuit model?
Much of the quantum computing literature focuses on the circuit model. Adiabatic quantum computing is not based on applying a sequence of unitary operators, but on changing a time-dependent ...
22
votes
1answer
2k views
How does the BosonSampling paper avoid easy classes of complex matrices?
In The computational complexity of linear optics (ECCC TR10-170), Scott Aaronson and Alex Arkhipov argue that if quantum computers can be efficiently simulated by classical computers then the ...
14
votes
1answer
749 views
Is there a quantum NC algorithm for computing GCD?
From the comments on one of my questions on MathOverflow
I get the feeling that the question regarding GCD being in $\mathsf{NC}$ vs. $\mathsf{P}$ is akin to the question regarding Integer ...
10
votes
2answers
415 views
Restricting entries of unitary operators to real numbers and universal gate sets
In Bernstein and Vazirani's seminal paper "Quantum Complexity Theory", they show that a $d$-dimensional unitary transformation can be efficiently approximated by a product of what they call "near-...
23
votes
5answers
683 views
Universal sets of gates for SU(3)?
In quantum computing we are often interested in cases where group of special unitary operators, G, for some d-dimensional system gives either the whole group SU(d) exactly or even just an ...
19
votes
3answers
797 views
Is there a Quantum equivalent of the Time hierarchy theorem ?
My favourite theorem in complexity theory is the Time hierarchy theorem. However, this was done in 1965.
I wanted to know then if there was anything similar for Quantum Computing.
Also, if not ...
10
votes
1answer
446 views
Span programs, witness size, and certificate complexity
A span program is a linear-algebraic way of specifying a boolean function introduced here. Recently, this model was used to show that the negative adversary method provides a tight characterization (...
7
votes
2answers
328 views
Given a subset of the hypercube and a copy translated by s, find s
Problem: Suppose we are given an $n$ element subset $A\subseteq\{0,1\}^d$ of the $d$ dimensional hypercube and a translated copy $B= A+s$ by some secret $s\in\{0,1\}^d$. Find $s$ as fast as possible ...
5
votes
1answer
229 views
Witness verifiable quantum advantage
Update: A slightly different version of this question has been answered here.
As far as I can see, a major issue with Google's recent quantum supremacy claim is that it is hard to verify the results.
...
8
votes
2answers
485 views
Understanding QMA
This question comes out of an answer Joe Fitzsimons gave to a different question. Most natural complexity classes have a one-line "intuitive description" that helps characterize core problems in that ...
5
votes
1answer
231 views
Are there problems that can be solved in time $2^{n-q^c}$ with $q$ qubits?
This is another attempt to formalize my former question on the topic.
I'm looking for a problem for which all known classical algorithms take exponential time, but given ANY number of few qubits (...
1
vote
1answer
124 views
Is unbounded quantum fanout operation experimentally feasible?
It is known that the "unbounded quantum fanout operation" is very powerful: (See, for example, Hoyer et al. : http://theoryofcomputing.org/articles/v001a005/v001a005.pdf).
In particular, it is known ...
10
votes
1answer
258 views
Lower bounds for quantum circuits using the geodesic framework
Some of us have been reading Michael Nielsen's paper on a geometric approach to using quantum lower bounds (in brief, the construction of a Finsler metric on $SU(2^n)$ such that the geodesic distance ...
7
votes
1answer
391 views
Quantum Money where not even the Bank can counterfeit
The Quantum Money system proposed in "Quantum Copy-Protection and Quantum Money" has the following properties:
The bank can produce bank notes in the form of quantum states.
Anyone can verify that ...
7
votes
2answers
459 views
Quantum query complexity and certificate complexity
A certificate for an input $x$ is a subset of bits $S \subseteq \{1,...,n\}$ such that for all inputs $y$, $(\forall i \in S \quad y_i = x_i) \rightarrow f(y) = f(x)$. Then $C_x(f)$ is the minimum ...
6
votes
2answers
352 views
Energy cost of adiabatic quantum computation
I'm not sure whether this question is completely on-topic, since it is a physics-related question. But I'll ask anyway and apologize if I'm off-topic.
In Adiabatic Quantum Computation is Equivalent ...
4
votes
0answers
184 views
Do the quantum communication complexity lower bounds hold when parties can send a “duplicated” qubits?
This question continues from the previous question where I mistakenly asked a question that is too general.
In quantum communication complexity, we always assume that Alice and Bob have unlimited ...
4
votes
6answers
5k views
Ternary (and beyond) computation and quantum computing?
Binary math is at the heart of most computing, in large part because of the ease with which two energy states can be achieved. I have always thought that having more states could improve computing ...
3
votes
1answer
158 views
How well can an arbitrary (unknown) quantum state be imperfectly cloned?
How well can an arbitrary unknown (quantum) state $\rvert \psi \rangle = \alpha\rvert 0 \rangle + \beta \rvert 1 \rangle$, be imperfectly/approximately cloned?
Given an unknown state ${\rvert \psi \...
3
votes
1answer
95 views
Questions about Farhi's pre-Adiabatic paper
I have been going through Eddie Farhi's 6-pages long pre-Adiabatic paper, An Analog Analogue of a Digital Quantum Computation.
I guess I understand most of the math and physics but I am struggling ...
0
votes
2answers
339 views
Are Alice and Bob allowed to copy qubits in quantum communication complexity model?
In quantum communication complexity, we always assume that Alice and Bob have unlimited computational power and are still prove lower bounds such as the $\Omega(n)$ lower bounds of parity.
What ...
