Quantum Entanglement towards scalable Quantum Computing | Quantum Science Philippines

## Quantum Entanglement towards scalable Quantum Computing

Gibson T. Maglasang

Quantum Physics, quantum information science and quantum computing are among the growing field of science and crowning intellectual achievements over the past century. Basically, it involves the storage, manipulation, teleportation and communication of information in quantum systems where great enhancements are possible due to entanglement. In this article, entanglement of a two fixed single-atom is demonstrated thru experiment. Moreover, the state of each of the two remotely located ion separated by one meter is measured in the unrotated and rotated by basis in order for the entanglement can be verified.

At the start of the experiment, each Ytterbium ion is trapped, laser cooled and initialized at the ground state [eq]|0 0\rangle[/eq]. Immediately then, the two ions are simultaneously excited by a 2-ps [eq]\sigma[/eq] polarized laser pulse to ensure that each ion emits at most a single photon. In addition, this process prepares the ion in the excited state with an excitation probability of [eq]P_{exc}=0.5[/eq]. The excited particle falls back to the one [eq]\left(|1-1\rangle\right)[/eq] or the other two qubit ground states [eq]\left(|10\rangle[/eq] or [eq]|\uparrow\rangle[/eq] and [eq]|00\rangle[/eq] or [eq]|\downarrow\rangle)[/eq] thereby emitting [eq]\pi[/eq]-polarized photon and [eq]\sigma[/eq]-polarized photon respectively. Each ion emits a photon whose frequency is perfectly correlated with the two atomic qubit states. It is then the atomic qubit and photon entanglement that will directly predict the entanglement of atoms. The spontaneously emitted photon from each ion are collected by the lenses, routed to the fiber-optic cable. It is further carried out to a 50-50 beam splitter where photons pass straight through the splitter or be reflected each with equal probability. Photons emerging from the splitter are then sent to a beam polarizer to filter out the [eq]\pi[/eq] decay channel. Simultaneous detection from both detectors (PMT) occurs only if the photons are in the antisymmetric state. Thus, revealing the odd parity wavefunction in the ion-ion entangled state [eq]\left(|\Psi\rangle_{atom}=|\uparrow\rangle_a|\downarrow\rangle_b-|\downarrow\rangle_a|\uparrow\rangle_b\right)[/eq].

Thus, a successful quantum entanglement between two remotely located ions is portrayed and such a network of remotely entangled ions or atoms could be of immense help towards scalable quantum computation and communication.