Nuclear spin qubits in a trapped-ion quantum computer (original) (raw)

Quantum information processing with trapped ions

2003

Experiments directed towards the development of a quantum computer based on trapped atomic ions are described briefly. We discuss the implementation of single qubit operations and gates between qubits. A geometric phase gate between two ion qubits is described. Limitations of the trapped-ion method such as those caused by Stark shifts and spontaneous emission are addressed. Finally, we describe a strategy to realize a large-scale device.

Realization of Universal Ion-Trap Quantum Computation with Decoherence-Free Qubits

Physical Review Letters, 2009

Any residual coupling of a quantum computer to the environment results in computational errors. Encoding quantum information in a so-called decoherence-free subspace provides means to avoid these errors. Despite tremendous progress in employing this technique to extend memory storage times by orders of magnitude, computation within such subspaces has been scarce. Here, we demonstrate the realization of a universal set of quantum gates acting on decoherence-free ion qubits. We combine these gates to realize the first controlled-NOT gate within a decoherence-free, scalable quantum computer.

Quantum computing with trapped ions

Physics Reports, 2008

Quantum computers hold the promise to solve certain computational task much more efficiently than classical computers. We review the recent experimental advancements towards a quantum computer with trapped ions. In particular, various implementations of qubits, quantum gates and some key experiments are discussed. Furthermore, we review some implementations of quantum algorithms such as a deterministic teleportation of quantum information and an error correction scheme.

Quantum Computation With Trapped Ions

Controllable Quantum States - Mesoscopic Superconductivity and Spintronics (MS+S2006) - Proceedings of the International Symposium, 2008

Trapped ions can be prepared, manipulated and analyzed with high fidelities. In addition, scalable ion trap architectures have been proposed (Kielpinski et al., Nature 417, 709 (2001).). Therefore trapped ions represent a promising approach to large scale quantum computing. Here we concentrate on the recent advancements of generating entangled states with small ion trap quantum computers. In particular, the creation of W-states with up to eight qubits and their characterization via state tomography is discussed.

Effective Quantum Spin Systems with Trapped Ions

Physical Review Letters, 2004

We show that the physical system consisting of trapped ions interacting with lasers may undergo a rich variety of quantum phase transitions. By changing the laser intensities and polarizations the dynamics of the internal states of the ions can be controlled, in such a way that an Ising or Heisenberglike interaction is induced between effective spins. Our scheme allows us to build an analogue quantum simulator of spin systems with trapped ions, and observe and analyze quantum phase transitions with unprecedented opportunities for the measurement and manipulation of spins.

A quantum information processor with trapped ions

New Journal of Physics, 2013

Quantum computers hold the promise to solve certain problems exponentially faster than their classical counterparts. Trapped atomic ions are among the physical systems in which building such a computing device seems viable. In this work we present a small-scale quantum information processor based on a string of 40 Ca + ions confined in a macroscopic linear Paul trap. We review our set of operations which includes non-coherent operations allowing us to realize arbitrary Markovian processes. In order to build a larger quantum information processor it is mandatory to reduce the error rate of the available operations which is only possible if the physics of the noise processes is well understood. We identify the dominant noise sources in our system and discuss their effects on different algorithms. Finally we demonstrate how our entire set of operations can be used to facilitate the implementation of algorithms by examples of the quantum Fourier transform and the quantum order finding algorithm.

Building blocks for a scalable quantum information processor based on trapped ions

2003

VJe describe the underlying concept and experimental demonstration of the basic building bloclts of a scalable quantum information processor archikcture using trapped ion-clubits. The trap structure is divided into many subregions. In eacl~ several ion-qubits can be trapped in complete isolation from all the other ion-qubits in the system. In a particular subregion, ion-qubits can either be st,ored as memory or subjected to individual rotations or multi-qubit gates. The ion-qubits are'guided through the array by appropriately switching control electrode potentials. Excess energy that is gained through the motion of ion-qubits in the array or other heating mecha.nisrr~s can be removed by sympathetic cooling of the ion-qubits with another ion species. The proposed architecture can be used in a highly parallel fashion, an imporlanl prerequisite for fault-tolerant quantum computation.

Erratum: Ion-trap Quantum Logic Using Long-Wavelength Radiation

Physical Review Letters - PHYS REV LETT, 2003

A quantum information processor is proposed that combines experimental techniques and technology successfully demonstrated either in nuclear magnetic resonance experiments or with trapped ions. An additional inhomogenenous magnetic field applied to an ion trap i) shifts individual ionic resonances (qubits), making them distinguishable by frequency, and, ii) mediates the coupling between internal and external degrees of freedom of trapped ions. This scheme permits one to individually address and coherently manipulate ions confined in an electrodynamic trap using radiation in the radiofrequency or microwave regime. 03.67.Lx, 42.50.Vk Quantum information processing (QIP) holds the promise of extending today's computing capabilities to problems that, with increasing complexity, require exponentially growing resources in time and/or the number of physical elements . The computation of properties of quantum systems themselves is particularly suited to be performed on a quantum computer, even on a device where logic operations can only be carried out with limited precision . Elements of quantum logic operations have been successfully demonstrated in experiments using ion traps , cavity quantum electrodynamics and in the case of nuclear magnetic resonance (NMR) even algorithms have been performed . Whereas quantum computation with nuclear spins in macroscopic ensembles can most likely not be extended beyond about 10 qubits (quantum mechanical two-state systems) [8], ion traps do not suffer from limited scalability in principle and represent a promising system to explore QIP experimentally. They can be employed to also investigate fundamental questions of quantum physics, for example related to decoherence [9] or multiparticle entanglement . However, they still pose considerable experimental challenges.

Individual Addressing of Trapped Ions and Coupling of Motional and Spin States Using rf Radiation

Physical Review Letters, 2009

Individual electrodynamically trapped and laser cooled ions are addressed in frequency space using radio-frequency radiation in the presence of a static magnetic field gradient. In addition, an interaction between motional and spin states induced by an rf field is demonstrated employing rfoptical double resonance spectroscopy. These are two essential experimental steps towards realizing a novel concept for implementing quantum simulations and quantum computing with trapped ions.

Scalable, High-Speed Measurement-Based Quantum Computer Using Trapped Ions

Physical Review Letters, 2009

We describe a scalable, high-speed, and robust architecture for measurement-based quantumcomputing with trapped ions. Measurement-based architectures offer a way to speed-up operation of a quantum computer significantly by parallelizing the slow entangling operations and transferring the speed requirement to fast measurement of qubits. We show that a 3D cluster state suitable for fault-tolerant measurement-based quantum computing can be implemented on a 2D array of ion traps. We propose the projective measurement of ions via multi-photon photoionization for nanosecond operation and discuss the viability of such a scheme for Ca ions.