Cryptography Stack Exchange
Cryptography Stack Exchange

Questions tagged [quantum-cryptography]

Quantum cryptography describes the use of quantum mechanical effects to perform cryptographic tasks. This is not to be confused with quantum computing or cryptanalysis techniques such as Shor's algorithm.

Quantum cryptography describes the use of quantum mechanical effects to perform cryptographic tasks, this method is alternatively known as quantum communication. These terms are interchangeable in most literature. This is not to be confused with quantum computing or cryptanalysis techniques such as Shor's algorithm.

Quantum Privacy Amplification (often called Quantum Key Distribution) is a sub-topic of Quantum Cryptography.

134 questions
11
votes
1 answer

Qubit / Qutrit - Is there a theoretical limit on how many orthogonal states a quantum bit has?

Seems like a quantum bit with $3$ orthogonal quantum states is called a qutrit - and they have been demonstrated practically. In comparison with $n$ qubits that have ~$2^{n}$ states, these have ~$3^{n}$ states. Is there a theoretical upper-limit on…
StefanS
  • 212
  • 1
  • 10
8
votes
2 answers

Could quantum computers "break" symmetric crypto-systems (e.g. AES)?

These days I'm reading about quantum computing and quantum cryptography which I've found extremely interesting. Well, I also read some blog posts of Bruce Schneier talking about how quantum computers threaten our current asymmetric crypto-systems.…
user6519
7
votes
1 answer

How do Latin squares relate to quantum cryptography?

About ten years ago I became interested in Latin squares. A friend who was at the Clay Institute at the time mentioned that applications for Latin squares were exploding, and that they were being utilized in quantum cryptography. I've found a paper…
DukeZhou
  • 173
  • 1
  • 6
5
votes
1 answer

Any implication of a Yale result to security of quantum cryptology?

Quantum key distribution depends, if I don't err, on (irreversible) damages done by MITM's measurements on qbits. Now news.yale.edu/2013/01/11/new-qubit-control-bodes-well-future-quantum-computing says: "The Yale physicists successfully devised a…
Mok-Kong Shen
  • 1,312
  • 1
  • 11
  • 15
5
votes
1 answer

Quantum computationally indistinguishable

We say two states $\sigma, \rho$ are computationally indistinguishable, if for efficient quantum algorithm $\mathbf{A}$, $|P(\mathbf{A}(\rho)=1)-P(\mathbf{A}(\sigma)=1)|$ is negligible. I want to show if the trace distance between above states are…
bluebird
  • 61
  • 2
3
votes
1 answer

BB84 - Bits needed to detect Eve's presence

From Quantum Computing: A Gentle Introduction: In the BB84 protocol, how many bits do Alice and Bob need to compare to have a 90% chance of detecting Eve's presence? I am having some trouble calculating this value. I understand that 50% of the…
vontell
  • 161
  • 8
2
votes
0 answers

Can quantum money exist?

Can a quantum money system exist in which bank (who possesses a secret key $k$) can create quantum states $S$ that anyone (in possession of public key $P$) can verify was issued by the bank without interacting with the bank, but nobody can spend…
Demi
  • 4,793
  • 1
  • 19
  • 39
2
votes
1 answer

BB84 Why does Bob generate a random key?

I am quite new to this stuff so this question might be trivial. I was reading about bb84 and, as I understood it, after Alice sends $\psi$ Bob chooses a random sequence $b'$ and makes a measurement in either $X$ or $Z$ according to $b'$. After Bob…
Francisco
  • 23
  • 2
2
votes
2 answers

Why a Unitary Matrix in Quantum Cryptography?

I've read that in Quantum circuits the matrix that encodes the transformation has to be unitary. I understand that it must preserve the norm of the resulting qubit, but what is the intuition behind it?
joaoaccarvalho
  • 31
  • 3
1
vote
0 answers

XOR & AND equation in quantum computing ... is it correct?

I'm trying to understand the following equality found in a paper of quantum key distribution Fully device independent quantum key distribution : $$a \oplus b = x \wedge y$$ As far as I know; $\oplus$ stands for lofic X-OR $\wedge$ stands for logic…
terence
  • 21
  • 2
1
vote
0 answers

Is ekert91 more secure than BB84?

I'm studying quantum cryptography and my question is "simple": Is the use of entangled states, like in the Ekert91 protocol, more secure than using not-entangled states like the BB84's ones? Is easier to detect eavesdropping in Ekert91?
Daniele Bianchi
  • 21
  • 2
1
vote
1 answer

what benefits quantum offer over classical parallelism

What is the benefits of quantum computing vs parallel processing using classical computer ? Can classical parallel processors outperform quantum computing ?
Glenn Camilleri
  • 61
  • 3
1
vote
1 answer

Router for Quantum key distribution

As far as I know QKD needs a quantum channel to send the photons. If anyone measures the photons they are useless. It sounds as if Alice needs a fiber optic cable all the way to Bob - or at least line-of-sight to Bob. So no wifi through walls. One…
Ole Tange
  • 331
  • 6
  • 14
1
vote
1 answer

How exactly works the quantum communication done by China?

This video and this article announced that spacial quantum communication were finally done using satellites. As a recap, when two particles are entangled, if a measurement is done to one of them, the appositive value results in the other particle.…
Luis Orantes
  • 132
  • 6
1
vote
1 answer

Could Grover's algorithm perform a search in N/2 for a match in a particular subset of a hash function preimage?

Suppose I first define some function f(x) where x is some unsigned 256-bit integer, and the function's output is a set of distinct strings of any length so that output set would be 2^256 unique strings, i.e. a bijection for the specified domain of…
bca-0353f40e
  • 133
  • 5
1
2