Experimental Quantum Networking Protocols via Four-Qubit Hyperentangled Dicke States

Abstract

We report the experimental demonstration of two quantum networking protocols, namely quantum 1→3 telecloning and open-destination teleportation, implemented using a four-qubit register whose state is encoded in a high-quality two-photon hyperentangled Dicke state. The state resource is characterized using criteria based on multipartite entanglement witnesses. We explore the characteristic entanglement-sharing structure of a Dicke state by implementing high-fidelity projections of the four-qubit resource onto lower-dimensional states. Our work demonstrates for the first time the usefulness of Dicke states for quantum information processing. PACS numbers: 42.50.Dv,03.67.Bg,42.50.Ex Networking offers the benefits of connectivity and sharing, often allowing for tasks that individuals are unable to accomplish on their own. This is known for computing, where grids of processors outperform the computational power of single machines or allow the storage of much larger databases. It should thus be expected that similar advantages are transferred to the realm of quantum information. Quantum networking, where a given task is pursued by a lattice of local nodes sharing (possibly entangled) quantum channels, is emerging as a realistic scenario for the implementation of quantum protocols requiring medium/large registers. Key examples of such approach are given by quantum repeaters [1], non-local gates [2], scheme for light-mediated interactions of distant matter qubits [3] and one-way quantum computation [4].In this scenario, photonics is playing an important role: the high reconfigurability of photonic setups and outstanding technical improvements have facilitated the birth of a new generation of experiments (performed both in bulk optics and, recently, in integrated photonic circuits [5]) that have demonstrated multi-photon quantum control towards high-fidelity computing with registers of a size inaccessible until only recently [6][7][8][9][10][11]. The design of complex interferometers and the exploitation of multiple degrees of freedom of a single photonic information carrier have enabled the production of interesting states, such as cluster/graph states, GHZ-like states and (phased) Dicke states [12][13][14], among others [15,16]. Dicke states have been successfully used to characterize multipartite entanglement close to fully symmetric states and its robustness to decoherence [14]. They are potentially useful resource for the implementation of protocols for distributed quantum communication such as quantum secret sharing [17], quantum telecloning (QTC) [18], and open destination teleportation (ODT) [19,20]. So far, such opportunities have only been examined theoretically and confirmed indirectly [12,13], leaving a full implementation of such protocols unaddressed.In this Letter, we report the experimental demonstration of 1→ 3 QTC and ODT of logical states using a four-qubit symmetric Dicke state with two excitations realized using a highquality hyperentangled (HE) photonic resource [14,21]. The entanglement-sharing ...

Transverse Entanglement of Biphotons

“…The case of continuous variables is especially appealing for quantum informational tasks because it allows access to a larger Hilbert space [5]. This is why entanglement in the transverse wavevectors of SPDC biphotons is currently in the focus of research [6,7,8,9,10]. Transverse entanglement can be understood in terms of the famous EPR scenario [11].…”

HeraldedW-state preparation using laser-designed superatoms

“…Higher excited collective states could be prepared using a sequence of probe pulses with different frequencies or by employing adiabatic preparation schemes [37,38]. Due to their multi-particle entanglement, higher excited Dicke states have many applications in metrology [39][40][41] and quantum information science [42,43]. Dicke states are not spin squeezed in the conventional sense [44,45], but nevertheless their entanglement is useful for sub-shot-noise interferomentry.…”

“…Thus, ideally one would like to prepare the state with m = N/2, corresponding to E N/2 in the notation used above. This state enables spectroscopy at the Heisenberg limit [8] and is also useful for quantum information processing tasks, such as 1 → (N − 1) telecloning or open-destination teleportation [42].…”

Spin squeezing and entanglement for an arbitrary spin

“…One of the most rapidly developing areas in quantum physics is creating larger and larger entangled quantum systems with photons, trapped ions, and cold neutral atoms [1][2][3][4][5][6][7][8][9][10][11][12]. Entangled states can be used for metrology in order to obtain a sensitivity higher than the shotnoise limit [13][14][15] and can also be used as a resource for certain quantum information processing tasks [16][17][18][19].…”