Measurement-Only Universal Blind Quantum Computation: Difference between revisions

==Outline==

The following Universal Blind Quantum Computation (UBQC) protocol uses the unique feature of [[Supplementary Information#Measurement Based Quantum Computation|Measurement Based Quantum Computation(MBQC)]] that separates the classical and quantum parts of a computation. Based on its counterpart Prepare and Send UBQC, this protocol requires Client to possess only a measurement device in order to perform blind quantum computation, hence the name 'Measurement Only UBQC'. The motivation behind this protocol lies in the fact that for several experimental setup like optical systems, measurement of a state is much easier than generation of a state. Presented below are two versions of the protocol. The first protocol needs only quantum communication throughout the protocol while second needs both quantum and classical throughout communication. These protocols are designed for classical input and output. It can be extended to quantum input/output by modifying the measurement angles of the Client according to Prepare and Send UBQC in order to hide her quantum output from the Server. Like all the other delegated quantum computing protocols, this protocol is also divided into two stages, Preparation and Computation.

*''Server’s preparation'' Server prepares the resource graph state required for MBQC by the Client.

*''Interaction and Client’s Computation'' Server sends single qubits of the prepared resource state to the Client who measures it in the basis required to carry out the quantum computation according to the measurement pattern in her mind. She records the outcomes and in the end of computation stage gets the result of her computation. This protocol is not tolerant to channel losses.

*''Server’s preparation'' This step remains the same as protocol 1a

*''Interaction and Client’s Computation'' Server prepares a Bell pair and sends one half of the Bell Pair to the Client. Client informs the Server if she receives the it or else if she doesn’t, Client asks Server to send it again. Client measures her share of entangled pair in a certain measurement basis depending on her MBQC pattern. Server then entangles his share of Bell pair and qubit of the resource state using CZ gate which transfers the gate/ measurement operated by Client to the resource qubit. Then he measures the resource qubit in X basis and communicates his classical measurement outcome to the Client. Client records it and uses it to compute her final outcome.

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