Narrow Results

We propose an alternative scheme to generate the GHZ states and cluster states for many trapped ions illuminated by a single laser tuned to the first lower vibrational sideband. The distinct advantage of the present scheme is that it does not use the vibrational mode as the data bus and only requires a single resonant interaction. Thus the present scheme is very simple and the interaction time is very short, which is important in view of decoherence.

We proposed a scheme to generate a multi-component squeezed coherent states with arbitrary coefficients on a line in phase space for multiple trapped ions radiated by a single standing-wave laser whose carrier frequency is tuned to the ions transition. In the scheme each ion does not need to be exactly positioned at the node of the standing wave. Furthermore, our scheme may allow the generation of a multi-component squeezed coherent states with large mean phonon number in a fast way by choosing a suitable laser intensity, which is important in view of de-coherence processes.

We present an alternative scheme to prepare entangled states of multiple trapped ions in thermal motion. In this scheme the vibrational degrees of freedom are only regarded as intermediate states and the ions exchange energy via the mediation of the vibration of the vibrational mode in coupling processes. The scheme is insensitive to both the initial vibrational state and heating if the system remains in the Lamb–Dicke regime. Since the effective Rabi frequency has a small dependence on the vibrational quantum number, the heating will have no direct effect on the internal state evolution. The scheme can also be used for the storage of entangled states.

In this letter, a procedure is proposed for reconstructing the motional quantum state of N trapped ions. Unlike other previous schemes, the present scheme works in the dispersive regime in the presence of dissipation. In our scheme, we show that it is possible to directly measure the quasiprobability distribution function corresponding to the motional coherent state in a trapped-ion system subjected to dissipation. We also provide an example of a motional Schrödinger cat state reconstruction to exemplify our procedure.

In this letter, a efficient scheme is proposed for the quantum secret encryption and decryption implementation for quantum secret sharing protocol with trapped ions in thermal motion, in which the effective Hamiltonian does not involve the external degree of freedom and thus the scheme is insensitive to the external state, allowing it to be thermal state. The proposed scheme requires no auxiliary states to assist intermediate atomic transitions and conditional quantum dynamics for quantum phase flip and quantum state diffusion. Besides, secret transmission using entanglement swapping also has been presented.

In this paper, we explore the nonlinear dynamics of two dipole-coupled-trapped ions in the Lamb–Dicke regime. The dynamics of the generated two-trapped-ions correlations under intrinsic decoherence is quantified by Bell function, the uncertainty-induced nonlocality, and the concurrence. We investigate the effects of the Lamb–Dicke nonlinearity, the intrinsic decoherence, and the two-trapped-ions coupling. It is found that the two-trapped-ions state has different nonlocal correlations. These correlations can be controlled. In the absence of decoherence, the nonlocal correlations can be enhanced by the Lamb–Dicke nonlinearity and the two-trapped-ions coupling. The stable value and the sudden death-birth phenomenon of the entanglement can be apperceived due to the increase of the Lamb–Dicke nonlinearity. The intrinsic decoherence reduces and stabilizes the nonlocal correlations. They are more pronounced with large Lamb–Dicke values. The decoherence effects are reduced by the strong Lamb–Dicke nonlinearity.

Trapped atomic ions have proven to be one of the most promising candidates for the realization of quantum computation due to their long trapping times, excellent coherence properties, and exquisite control of the internal atomic states. Integrating ions (quantum memory) with photons (distance link) offers a unique path to large-scale quantum computation and long-distance quantum communication. In this article, we present a detailed review of the experimental implementation of a heralded photon-mediated quantum gate between remote ions, and the employment of this gate to perform a teleportation protocol between two ions separated by a distance of about one meter.

High-resolution laser spectroscopy and quantum information processing have a great deal in common. For both applications, ions held in electromagnetic traps can be employed, the ions' quantum state being manipulated by lasers. Quantum superposition states play a key role, and information about the experiment is inferred from a quantum state measurement that projects the ions' superposition state onto one of the basis states. In this paper, we discuss applications of Ramsey spectroscopy for quantum information processing and show that techniques developed in the context of quantum information processing find useful applications in atomic precision spectroscopy.

Computers that operate with quantum processes promise unprecedented computational power for some algorithms, much more than could be obtained by classical machines. The implementation of such a quantum computer requires the precise control and manipulation of individual quantum systems, a task that can be achieved by quantum optical means and the use of precision laser spectroscopy.

Optical spectroscopy has matured to the most precise measurement tool in physics thanks to advances in single ion trapping and the possibility to directly measure the frequency of laser light. However, almost 50 years after the invention of the laser the spectral region that can be investigated in this way is still restricted to wavelengths below the near ultraviolet. The much larger spectral band of the extreme ultraviolet (XUV), where many fundamental transitions of say hydrogen like ions reside, is thus far unexplored by high precision laser spectroscopy. One possible route to narrow band radiation in this region could be the use of high order harmonics generated with short laser pulses of high repetition rate focused in a gas jet. Meanwhile µW power levels in the XUV at multi-MHz repetition rates have been demonstrated which are the main prerequisites for this method. The 1S-2S two photon transition at 60 nm in singly ionized helium is a rewarding candidate because it allows sensitive tests of quantum electrodynamics.