Unconditional quantum teleportation between distant solid-state quantum bits

Abstract

Realizing robust quantum information transfer between long-lived qubit registers is a key challenge for quantum information science and technology. Here we demonstrate unconditional teleportation of arbitrary quantum states between diamond spin qubits separated by 3 meters. We prepare the teleporter through photon-mediated heralded entanglement between two distant electron spins and subsequently encode the source qubit in a single nuclear spin. By realizing a fully deterministic Bell-state measurement combined with real-time feed-forward we achieve teleportation in each attempt while obtaining an average state fidelity exceeding the classical limit. These results establish diamond spin qubits as a prime candidate for the realization of quantum networks for quantum communication and network-based quantum computing.The reliable transmission of quantum states between remote locations is a major open challenge in quantum science today. Quantum state transfer between nodes containing long-lived qubits [1][2][3] can extend quantum key distribution to long distances [4], enable blind quantum computing in the cloud [5] and serve as a critical primitive for a future quantum network [6]. When provided with a single copy of an unknown quantum state, directly sending the state in a carrier such as a photon is unreliable due to inevitable losses. Creating and sending several copies of the state to counteract such transmission losses is impossible by the no-cloning theorem [7]. Nevertheless, quantum information can be faithfully transmitted over arbitrary distances through quantum teleportation provided the network parties (named "Alice" and "Bob") have previously established a shared entangled state and can communicate classically [8][9][10][11].The teleportation protocol is sketched in Fig. 1A. At the start, Alice is in possession of the state to be teleported (qubit 1) which is most generally given by |ψ = α|0 + β|1 . Alice and Bob each have one qubit of an entangled pair (qubits 2 and 3) in the joint state |ΨThe combined state of all three qubits can be rewritten aswhere |Φ ± = (|00 ± |11 )/ √ 2 and |Ψ ± = (|01 ± |10 )/ √ 2 are the four Bell states. To teleport the quantum state Alice performs a joint measurement on her * Present address: Department of Applied Physics, Yale University, New Haven, CT 06511, USA † r.hanson@tudelft.nl qubits (qubits 1 and 2) in the Bell basis, projecting Bob's qubit into a state that is equal to |ψ up to a unitary operation that depends on the outcome of Alice's measurement. Alice sends the outcome via a classical communication channel to Bob, who can then recover the original state by applying the corresponding local transformation.Because the source qubit state always disappears on Alice's side, it is irrevocably lost whenever the protocol fails. Therefore, to ensure that each qubit state inserted into the teleporter unconditionally re-appears on Bob's side, Alice must be able to distinguish between all four Bell states in a single shot and Bob has to preserve the coherence of the target q...

Coherent spin control of a nanocavity-enhanced qubit in diamond

“…21), so even higher entanglement rates are achievable. Recently achieved quantum teleportation rates based on differentiating the excited spin states with high selectivity would also significantly benefit from this speed-up 22 . Another entanglement protocol relies on state-dependent reflectivity (resonant scattering) of an incoming photon on the cavity 23 .…”

Entanglement dynamics of quantum oscillators nonlinearly coupled to thermal environments

“…For a bipartite system with no inter-mode coupling, it follows that the same parity conservation will, at T = 0, bring the system into a general steady state ρ(∞) = P 00 |00 00| + P 11 |11 11| + ρ 01,10 |01 10| +ρ 10,10 |10 10| + ρ 00,11 |00 11| + ρ 00,01 |00 01| + ρ 00,10 |00 10| + ρ 01,10 |01 10| +ρ 01,11 |01 11| + ρ 10,11 |10 11| + H.c. , (13) with matrix elements ρ ni,mj determined by the initial state. The particular initial state (12) leads to a steady state of the form (13) where several elements are zero, reducing it to ρ(∞) = P 00 |00 00| + P 11 |11 11| + (ρ 00,11 |00 11| + H.c) .…”

“…Here, in the light of previous studies on linearly damped oscillator systems, we investigate how NLD affects the asymptotic state behavior of initially entangled states. For the latter we choose two-mode squeezed vacuum states [13,14,33,34]. These states are entangled, Gaussian states, which approach the maximally entangled EPRstate by an increase of the squeezing parameter.…”

“…Problems relating to entanglement creation and manipulation are of importance for a broad range of questions related to quantum information science [3], like quantum cryptography [4], quantum dense coding [5], quantum computation algorithms [6] and quantum state teleportation [7][8][9]. In particular, recent experimental advances [10][11][12][13] pave the way for entanglement-based technology.…”

Single pairs of time-bin-entangled photons

“…We overcome the need of a metastable state and avoid the multiphoton emission probability p 2 that is inherent to all previous implementations of time-bin-entanglement generation. Our source opens up possibilities for the transfer of spin-photon entanglement [26][27][28][29] over long distances, hyperentanglement [30], quantum dense coding [31], and deterministic entanglement purification [32], and could be developed further for integration in compact and scalable quantum information devices.…”