Editing Prepare and Measure Quantum Digital Signature (section)

==Further Information==
The protocol under discussion (1) was the first version of Quantum Digital Signatures with only prepare and measure QKD components. The assumption authenticated quantum channel would render it useless as authenticated quantum channel is a more complex protocol. Thus in (6), a variant of this protocol overcomes this assumption by using a Key generation protocol (not QKD) for authentication where, instead of Seller, Buyer and Verifier sends quantum public keys to the Seller to measure in randomly chosen basis and generate her private keys. This variant is the '''simplest''' QDS protocol from the point of view of implementation. Following description for various papers on QDS protocols and their variants have been written keeping in mind the hardware requirements, assumptions, security and method used. One of the papers discusses generalisation of protocols to more than 3 parties and another one discusses security for iterating in case of sending multiple bits.
*'''Theoretical Papers'''
#[https://arxiv.org/abs/1403.5551  WDKA (2015)] above example
#[https://arxiv.org/abs/1309.1375 DWA (2013)] first QDS scheme without quantum memory based on [[Coherent State Comparison]]. 
##'''Requires''' [[Coherent States]], authenticated quantum and classical channels, [[multiports]], [[Unambiguous State Discrimination (USD)]] (State Elimination), no symmetrisation required. 
##'''Security:''' Information-theoretic
#[https://journals.aps.org/pra/abstract/10.1103/PhysRevA.90.042335 AL (2014)] establishes coherent state mapping of (2). Replaces SWAP Test with beam splitters. Uses [[Unambiguous State Discrimination (USD)]] (State Elimination). 
##'''Requires''' [[Coherent States|Phase encoded Coherent states]], [[Balanced Beam Splitters]]. 
##No explicit security proof provided.
#[https://arxiv.org/abs/1505.07509 AWA (2015)] security proof for generalisation of [https://arxiv.org/abs/1403.5551  WDKA (2015)] and [https://arxiv.org/abs/1309.1375 DWA (2013)] to more than two recipients case.
#[https://arxiv.org/abs/1507.03333 YFC (2016)] first QDS scheme without authenticated (trusted) quantum channels. Demonstrates one protocol with two implementation, two copies of single photon method and  decoy state method. First uses single qubit photons in three bases; Private key: classical description of states, Public key: pair of [[non-orthogonal states]] in any two of the three bases. 
##'''Requires''' authenticated classical channels, [[polarisation measurement]] in three bases, [[Unambiguous State Discrimination (USD)]] (State Elimination), uses quantum correlations to check authentication.  Decoy State method uses [[Coherent States|phase-randomised weak coherent states]], [[50:50 Beam Splitter (BS)]]. 
##Security: [[Information-theoretic]].
#[https://arxiv.org/abs/1507.02975  AWKA (2015)] QDS scheme without authenticated quantum channels using parameter estimation phase. Uses a Key Generation Protocol (KGP) where noise threshold for Seller-Buyer and Seller-Verifier is better than when distilling secret key from QKD. Seller sends different key to Buyer and Verifier using KGP. This anomaly is justifiable due to symmetrisation.
##'''Requires''' authenticated classical channels, [[Decoy State QKD]] setup. 
##Security: [[Information-theoretic]].
#[https://www.nature.com/articles/srep09231 WCRZ (2015)] demonstrates sending multi-bit classical messages using [https://arxiv.org/abs/1507.02975  AWKA (2015)] or other similar protocols.</br>
#[http://iopscience.iop.org/article/10.1088/1742-6596/766/1/012021 MH (2016)] security proof for generalisation of [https://arxiv.org/abs/1507.02975  AWKA (2015)] to more than two recipients case.
*'''Experimental Papers'''
#[https://physics.aps.org/featured-article-pdf/10.1103/PhysRevLett.113.040502 Collins et al (2014)] first experimental demonstration of a QDS scheme without quantum memory, implements a variant of [https://arxiv.org/abs/1309.1375 DWA (2013)]. Uses unambiguous state elimination (USE) instead of unambiguous state determination (USD)
##Per half-bit message: rate=1.4 bits per second, security bound=0.01%, Length of the key (L)= <math>10^{13}</math>
#[https://arxiv.org/abs/1509.07827 Donaldson et al (2015)] Implements [https://arxiv.org/abs/1403.5551  WDKA (2015)].
##Uses [[Coherent States|phase encoded coherent states]]
## Per half a bit message: Transmission Distance(d)=500 m, Length of the key(L)=<math>1.93*10^9</math> for security 0.01%, estimated time to sign (<math>t</math>)=20 seconds, channel loss= 2.2 dBkm<math>^{-1}</math> at <math>\lambda=850m</math>
#[https://www.ncbi.nlm.nih.gov/pubmed/27805641 Collins et al (2016)] Implements modified [https://arxiv.org/abs/1507.02975  AWKA (2015)]
##Uses differential phase shift QKD for QDS
## message signing rate= 1 or 2 bits per second for security parameter=0.0001, Length of keys(L)=2Mbits, Transmission distance=90 km, QBER=1.08%, attenuation=0.32 dBkm<math>^{-1}</math>
#[https://www.nature.com/articles/s41598-017-03401-9 Collins et al (2017)] Implements modified [https://www.researchgate.net/publication/280034032_Secure_Quantum_Signatures_Using_Insecure_Quantum_Channels  AWKA (2015)] using DPS QKD 
##Per half a bit message: Channel loss=43 dB, transmission distance= 132 km, security parameter=<math>10^{-4}</math>
#[https://journals.aps.org/pra/abstract/10.1103/PhysRevA.95.032334 Yin et al (2018)] Implements decoy state QDS scheme in [https://arxiv.org/abs/1507.03333 YFC (2016)] 
##Uses nanowire single photon detectors (SNSPD), BB84 state encoding, decoy state modulation.
## Signed a 32 bit message "USTC" over transmission distance 102 km, authentication threshold =2%, verification threshold=0.6%, security bound parameter=<math>10^{-5}</math>, estimated time=360 seconds for one bit message
#[https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.10.034033 Zhang et al (2018)] Implements a [[Decoy State QKD|passive decoy state]] protocol which uses Passive BB84 Key Generation protocol (KGP) to share public keys from Bob and Charlie to Alice.
## Uses parametric down-conversion (PDC) source, secure to coherent attacks
## Per half a bit message:Transmission Distance(d)=100 km, QBER(%)=<math>2.95%-3.28%</math> for security parameter=<math>10^{-4}</math>, attenuation=45.8 dB at 200 km estimated time to sign (<math>t</math>)=7 seconds



<div style='text-align: right;'>''*contributed by Shraddha Singh''</div>