Search results for "Superdense coding"
showing 9 items of 9 documents
Efficient protocol for qubit initialization with a tunable environment
2017
We propose an efficient qubit initialization protocol based on a dissipative environment that can be dynamically adjusted. Here the qubit is coupled to a thermal bath through a tunable harmonic oscillator. On-demand initialization is achieved by sweeping the oscillator rapidly into resonance with the qubit. This resonant coupling with the engineered environment induces fast relaxation to the ground state of the system, and a consecutive rapid sweep back to off resonance guarantees weak excess dissipation during quantum computations. We solve the corresponding quantum dynamics using a Markovian master equation for the reduced density operator of the qubit-bath system. This allows us to optim…
Continuous-Variable Quantum Teleportation of Discrete-Variable Entanglement
2013
We experimentally demonstrate continuous-variable quantum teleportation of discrete-variable entanglement in the form of a split single photon. Entanglement is optimally transferred for finite resource squeezing by tuning the teleporter's feedforward gain.
Hybrid quantum teleportation
2013
Quantum teleportation allows for the transfer of arbitrary, in principle, unknown quantum states from a sender to a spatially distant receiver, who share an entangled state and can communicate classically. It is the essence of many sophisticated protocols for quantum communication and computation. In order to realize flying qubits in these schemes, photons are an optimal choice. However, teleporting a photonic qubit has been limited due to experimental inefficiencies and restrictions. Major disadvantages have been the probabilistic nature of both entangled resource states and linear-optics Bell-state measurements (BSM), as well as the need for post-selecting the successful events by destroy…
Gain tuning for continuous-variable quantum teleportation of discrete-variable states
2013
We present a general formalism to describe continuous-variable (CV) quantum teleportation of discrete-variable (DV) states with gain tuning, taking into account experimental imperfections. Here the teleportation output is given by independently transforming each density matrix element of the initial state. This formalism allows us to accurately model various teleportation experiments and to analyze the gain dependence of their respective figures of merit. We apply our formalism to the recent experiment of CV teleportation of qubits [S. Takeda et al., Nature 500, 315 (2013)] and investigate the optimal gain for the transfer fidelity. We also propose and model an experiment for CV teleportati…
Vacuum Suppression in Gain-tuned Continuous-Variable Quantum Teleportation of a Single Photon by Conditioning on Sender
2014
We experimentally demonstrate bolstering the strength of gain-tuned continuous variable quantum teleportation of a single photon by conditioning on the sender's measurement results to eliminate excess vacuum contamination in the output.
Long-distance entanglement and quantum teleportation in coupled-cavity arrays
2009
We introduce quantum spin models whose ground states allow for sizeable entanglement between distant spins. We discuss how spin models with global end-to-end entanglement realize quantum teleportation channels with optimal compromise between scalability and resilience to thermal decoherence, and can be implemented straightforwardly in suitably engineered arrays of coupled optical cavities.
Deterministic quantum teleportation of photonic quantum bits by a hybrid technique.
2014
The continuous-variable teleportation of a discrete-variable, photonic qubit is deterministic and allows for faithful qubit transfer even with imperfect continuous-variable entangled states: for four qubits, the overall transfer fidelities all exceed the classical limit of teleportation. Quantum teleportation is one of the most important elementary protocols in quantum information processing. Previous studies have achieved quantum teleportation, but usually randomly and at low rates. Two groups reporting in this issue of Nature have used contrasting methods to achieve the same aim —more efficient quantum teleportation. Takeda et al. describe the experimental realization of fully determinist…
Quantum state transfer between light and matter via teleportation
2009
Quantum teleportation is an interesting feature of quantum mechanics. Entanglement is used as a link between two remote locations to transfer a quantum state without physically sending it – a process that cannot be realized utilizing merely classical tools. Furthermore it has become evident that teleportation is also an important element of future quantum networks and it can be an ingredient for quantum computation. This article reports for the first time the teleportation from light to atoms. In the experiment discussed, the quantum state of a light beam is transferred to an atomic ensemble. The key element of light-atom entanglement created via a dispersive interaction lays the foundation…
Ultrafast Long-Distance Quantum Communication with Static Linear Optics
2015
We propose a projection measurement onto encoded Bell states with a static network of linear optical elements. By increasing the size of the quantum error correction code, both Bell measurement efficiency and photon-loss tolerance can be made arbitrarily high at the same time. As a main application, we show that all-optical quantum communication over large distances with communication rates similar to those of classical communication is possible solely based on local state teleportations using optical sources of encoded Bell states, fixed arrays of beam splitters, and photon detectors. As another application, generalizing state teleportation to gate teleportation for quantum computation, we…