Quantum Information Processing with Ions and Photons

Christopher R. Monroe

B. G. Norton, Moji Ghadimi, Valdis Blūms +1 more

Quantum information processing (QIP) promises to radically change the outlook for secure communications, both by breaking existing cryptographic protocols and offering new quantum protocols in their place. A promising technology for QIP uses arrays of atomic ions that are trapped in ultrahigh vacuum and manipulated by lasers. Over the last several years, work in my research group has led to the demonstration of a monolithically integrated, scalable optical interconnect for trapped-ion QIP. Our interconnect collects single photons from trapped ions using a diffractive mirror array, which is fabricated directly on a chip-type ion trap using a CMOS-compatible process. Based on this interconnect, we have proposed an architecture that couples trapped ion arrays with photonic integrated circuits to achieve compatibility with current telecom networks. Such tightly integrated, highly parallel systems open the prospect of long-distance quantum cryptography.

Jungsang Kim, Emily Mount, So-Young Baek +9 more

We present a scalable approach to quantum information processing utilizing trapped ions and photons. Ions trapped in microfabricated surface traps provide a practical platform for realizing quantum networks of distributed computing nodes and quantum repeaters.

Timo Koerber

Nicklas Ohlsson

In this thesis, aspects of the use of cryogenically cooled rare-earth-ion-doped crystals in the fields of quantum optics and quantum information processing are addressed. The experiments and theoretical considerations referred to in this thesis are based on the coherent transient interaction between light and the ions in the crystals. A photon echo experiment has been performed where faint optical pulses were accumulated in the crystal. In this experiment, the possibility of single photons acting as two of the optical fields in the photon echo process was investigated. Different aspects on the experiment, which can be viewed as delayed self-interference of a single photon, are discussed in this thesis. A scheme for the possible implementation of quantum information processing in rare-earth-ion-doped crystals is presented. A key feature in this scheme is that small groups of ions, which can be optically manipulated and which interact in a controlled way, can be extracted from a collection of randomly positioned ions in the crystal host. Initial experimental investigations of the scheme, indicating the possibility of implementing quantum gates, are also presented in this thesis. In another experiment, the application of magnetic fields of up to 5 T was seen to increase the lifetime of information stored as frequency-dependent modulation of the population of thulium ions doped into a YAG crystal by several orders of magnitude. This mechanism might be useful in data storage and information processing applications. An experiment in which the same type of crystal was used as the active medium in a photon-echo-based pulse compression experiment, where microsecond long pulses were compressed to nanosecond duration using frequency-chirped light pulses, is also reported in this thesis.

Christian F. Roos