Secure Client- Server Delegated Computation: Difference between revisions

== Functionality Description==

Delegated Computation is the task of assigning quantum computation to an untrusted device while maintaining privacy of the computation. Protocols under this functionality are commonly called ClientServer protocols. Delegated Quantum Computation (DQC) protocols involve partially/fully classical Client delegate a quantum computation task to a fully powerful quantum Server. All DQC protocols involve three main stages, Prepataion Stage, Computation Stage, Output Correction Stage. The roles of Client and Server in the different stages may differ according to the type of communication used. It can be performed via classical online/offline and quantum online/offline communication. It can be verifiable or non-verifiable. Hence, it is classified as follows.

===Classical Online Communication-Quantum Offline Communication===

It involves a partially quantum Client perform a one time quantum communication to send input to the Server, in the preparation Stage and then to receive outputs from the Server, during output correction. The Client and Server then exchange classical messages during the computation phase. Universal Blind Quantum Computation (UBQC) is a protocol falling under this category. In this protocol Client hides his input, output and computation from the Server using [[Supplementary Information#Measurement Based Quantum Computation|MBQC]] by sending hidden quantum states to the Server. UBQC protocols can be realised by a [[Prepare and Send-Universal Blind Quantum Computation|Prepare and Send UBQC]] protocol where client prepares and sends the input states to the Server. If the task performed by the Server can be verified by the Client, the protocol is Verifiable Universal Blind Quantum Computation (VUBQC). Same as UBQC, VUBQC can also be realised by [[Prepare and Send Verifiable Universal Blind Quantum Computation|Prepare and Send VUBQC]].

===Classical Offline Communication-No Quantum Communication===

It involves a fully classical Client assign quantum computation to a Server on her classical input/output using only classical communication during the preparation stage and output correction. There is no communication between the two parties during computation stage. It uses only classical [[Supplementary Information#Homomorphic Encryption|HE]] and no quantum gadgets to realize a quantum functionality. Quantum offline communication would be needed in case of quantum input/output. Protocols falling under this category are quantum capable Classical Fully Homomorphic Encryption [[Classical Fully Homomorphic Encryption for Quantum Circuits|(FHE) for Quantum Circuits]]. A verification of FHE for Quantum Circuits protocol is still an open question.  

  '''Tags:''' [[Two Party Protocols|Two Party]], [[Universal Task|Universal Task]], [[Quantum Functionality|Quantum Functionality]], [[Multiparty Delegated Quantum Computation|Multiparty Delegated Quantum Computation]], [[Quantum Enhanced Classical Delegated Computation|Quantum Enhanced Classical Delegated Computing]]