One-Qubit Rotation

Chui‐Ping Yang, Julio R. Gea-Banacloche

We show how an arbitrary qubit rotation can be teleported, albeit probabilistically, using one e-bit of entanglement and one classical bit. We use this to present a scheme for implementing quantum secret sharing. The scheme operates essentially by sending a `secret' rotated qubit of information to several users, who need to cooperate in order to recover the original qubit.

Subhash C. Kak

Lajos Diósi

Hong LU, LiBing CHEN

We show how a many-to-one and a one-to-many controlled remote quantum rotations (CRQRs) can be implemented deterministically and exactly by using partially entangled quantum channels. Firstly, we present a theoretical scheme for a N -to-1 CRQR, in which the quantum rotations initially distributed in N spatially separated qubits can be exactly and deterministically performed onto a remote single qubit via two partially entangled ( N + M +1)-qubit Greenberger-Horne-Zeilinger (GHZ) states without performing any global operations. The feature of this scheme is that, apart from N senders and a receiver, M agents are included in the process as controllers. Should any one of the M agents not cooperate, the receiver could not gain the original rotations. Then, we design another scheme for implementing a 1-to- N CRIC with unit fidelity and unit probability by employing a partially entangled (2 M + N +1)-qubit Einstein-Podolsky-Rosen (EPR)-GHZ state or K partially entangled ( M +2)-qubit GHZ states, in which a quantum rotation can be divided into N pieces ( N K ) and performed from a sender onto N distant receivers via the control of M agents in a quantum network. In these schemes, the senders (or the receivers, or the controllers) local positive operator valued measurement (POVM) lies at the heart. We construct the required POVMs. The fact that deterministic and exact implementation of a many-to-one or a one-to-many CRQR could be realized using partially entangled quantum channel is notable. These schemes can be used to quantum secret sharing, quantum voting, and so on. They definitely have the strong security.

Lajos Diósi

Yun-Pil Shim, Jianjia Fei, Sangchul Oh +2 more

Any single-qubit unitary operation or quantum gate can be considered a rotation. Typical experimental implementations of single-qubit gates involve two or three fixed rotation axes, and up to three rotation steps. Here we show that, if the rotation axes can be tuned arbitrarily in a fixed plane, then two rotation steps are sufficient for implementing a single-qubit gate, and one rotation step is sufficient for implementing a state transformation. The results are relevant for "exchange-only" logical qubits encoded in three-spin blocks, which are important for universal quantum computation in decoherence free subsystems and subspaces.