Entangled photonic qutrits

Jeremy L. O’Brien, Akira Furusawa, Jelena Vuckovic A

S. P. Kulik, Stanislav S. Straupe

In this paper we discuss physical aspects of entanglement in biphoton-based qutrits and ququarts, taking into account the bosonic correlations due to the indistinguishability of photons. We show that two apparently different types of entanglement in these systems, 'entanglement of modes' and 'entanglement of photons', are in fact closely related to each other. The latter is to a remarkable extent connected with the degree of polarization of two-photon light. Specifically, we demonstrate that a beamsplitter and subsequent post-selection using a coincidence circuit converts 'entanglement of photons' of a qutrit into 'entanglement of modes' of a ququart.

Chui‐Ping Yang, Qi-Ping Su, Siyuan Han

We propose an efficient method to generate a Greenberger-Horne-Zeilinger entangled state of $n$ photons in $n$ microwave cavities (or resonators) via resonant interaction to a single superconducting qutrit. The deployment of a qutrit, instead of a qubit, as the coupler enables us to use resonant interactions exclusively for all qutrit-cavity and qutrit-pulse operations. This unique approach significantly shortens the time of operation, which is advantageous for reducing the adverse effects of qutrit decoherence and cavity decay on the fidelity of the protocol. Furthermore, the protocol involves no measurement on either the state of the qutrit or cavity photons. We also show that the protocol can be generalized to other systems by replacing the superconducting qutrit coupler with different types of physical qutrits, such as an atom in the case of cavity QED, to accomplish the same task.

B. P. Lanyon, Till J. Weinhold, Nathan K. Langford +4 more

Quantum information carriers with higher dimension than the canonical qubit offer significant advantages. However, manipulating such systems is extremely difficult. We show how measurement-induced nonlinearities can dramatically extend the range of possible transforms on biphotonic qutrits-three-level quantum systems formed by the polarization of two photons in the same spatiotemporal mode. We fully characterize the biphoton-photon entanglement that underpins our technique, thereby realizing the first instance of qubit-qutrit entanglement. We discuss an extension of our technique to generate qutrit-qutrit entanglement and to manipulate any bosonic encoding of quantum information.