6
votes
Accepted
Can quantum state tomography break bb84?
No, weak measurement and quantum tomography don't break BB84.
I recommend that you create an explicit quantum circuit that implements the weak measurement or the quantum tomography, and check for ...
- 33.3k
4
votes
Can quantum state tomography break bb84?
Tomography generally speaking uses a collection of measurements to reproduce an underlying state. So you experimentally reproduce the same situation over and over, collect statistics and find the most ...
- 1,099
3
votes
Accepted
Misunderstanding of QKD BB84 protocol
This looks like a mistake in the image to me (or a reflection of Alice and Bob using faulty procedures to convert bits to qubits and vice versa, which seems much less likely).
Under ideal conditions, ...
- 8,785
3
votes
Accepted
How to correctly describe state preparation?
For applications such as BB84, it really doesn't matter which of the two descriptions you use, because from everybody's perspective apart from Alice, they do not have access to the first system, and ...
- 55.7k
3
votes
Accepted
What is the difference between CV QKD and DV QKD?
It's the dimension of the Hilbert spaces. In DV-QKD you have a finite dimensional Hilbert space (like a qubit). Thus your measurement outcomes come from a finite set. On the other hand a CV-QKD ...
- 5,355
3
votes
Non maximally entangled states for QKD
In schemes like E91, the idea behind using an entangled state is that:
in a particular measurement basis (for both parties), the measurement outcomes are perfectly correlated but completely random (...
- 55.7k
2
votes
Is there any programming project that implements one QKD protocol or demonstrates it?
Yes, there are such projects! The codes are on GitHub, alongside an explanation of the protocols, which makes understanding the protocols like a walk in the park!
Here's the link: https://github.com/...
- 21
2
votes
How do I compare the secret key rate (kbps) with the secret key rate per channel use?
Indeed, the PLOB bound is an ultimate upper bound for repeaterless quantum communications, and is thus derived by averaging over $n\rightarrow \infty$ uses of the communications channel - Hence why ...
- 101
2
votes
Accepted
Ekert's QKD protocol with Eve ( hacker ) sending random mixture of qubit pairs in the states |00>, |11>, |++>, |-->
Your interpretation is incorrect.
In the original scheme without Eve, Alice and Bob share the state
$$
|\Phi^+ \rangle = \frac{1}{\sqrt{2}}(|00\rangle + |11\rangle) = \frac{1}{\sqrt{2}}(|++\rangle + |-...
- 6,711
2
votes
What is the difference between CV QKD and DV QKD?
One example to understand it, if someone finds it useful, is the following:
Most QKD is done by sending light through a channel. In DV-QKD we send single photons through the channel, one at a time. We ...
- 31
2
votes
Accepted
Doubt in Simple proof of Security of the BB84 QKD
I'm not sure that I would claim the two situations are entirely equivalent - if Alice and Bob share Bell pairs, there are extra things they could do (e.g. testing Bell inequalities), but in terms of ...
- 55.7k
2
votes
Major Security proofs available for Device-Independent QKD
The progress in DIQKD security proofs has been quite rapid in recent years. In particular, the approach of Vazirani and Vidick is no longer what the community uses.
The two major approaches that I ...
- 5,355
1
vote
How can entanglement deal with individual attack in QKD?
This is indeed a problem that can't be ignored when stepping from theory to implementation.
Physical realisations for photon scattering should provide a rate as close as possible to exact single ...
- 1,566
1
vote
Accepted
Why is applying a Hadamard transform useful in the entanglement-based version of BB84
Eve can wait until Alice makes the announcement, but the announcement only happens once Bob has received the qubit, so in the simplest attack (where Eve just measures the qubit and then sends it on to ...
- 401
1
vote
Would QKD break down if you have the receiver box of Bob?
The problem you present is the man-in-the-middle attack. What if Eve supplants Bob using the same hardware? She would get a shared key Alice-Eve. She could do the same with Bob, acting like Alice. She ...
- 31
1
vote
Do quantum computers have any security risks associated with them?
Quantum computing is so far away from anything that would ever have to worry about security risks.
It's very much debated how far away we are from having a quantum computer, but I personally think it'...
- 1,099
1
vote
How are Franson Interferometers used to prove security in Photonic QKD Experiments?
What a Franson interferometer does is to superpose two-photon wavepackets generated at different times (within the coherence time of the pump, supposing we are generating a pair of entangled photons ...
1
vote
Accepted
In the BB84 protocol, for what error thresholds can Alice and Bob not establish secure bits?
As far as I know, the error threshold depends on the security proof. Meaning, BB84 has different security proofs, each with different assumptions, resulting in different security threshold. The '...
- 1,775
1
vote
What authentication protocol to use for BB84 and other QKD protocols?
In classical cryptography, the Diffie-Hellman key exchange is also susceptible to a man-in-the-middle attack, and to get around that, we use a digital signature algorithm, like RSA or ECDSA.
You can ...
- 41
1
vote
Non maximally entangled states for QKD
They did use them in the Vienna loophole-free Bell test, which is a pre-condition for implementing DIQKD. Their benefit is that you can do a loophole-free violation of the CHSH inequality efficiency ...
- 2,372
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