Quantum Information Processing, Vol. 3, Nos. 1–5, October 2004 (© 2004)
Ion Trap Quantum Computing with Ca
C. F. Roos,
and F. Schmidt-Kaler
Received April 6, 2004; accepted April 22, 2004
The scheme of an ion trap quantum computer is described and the implementation
of quantum gate operations with trapped Ca
ions is discussed. Quantum infor-
mation processing with Ca
ions is exempliﬁed with several recent experiments
investigating entanglement of ions.
KEY WORDS: Quantum computation; trapped ions; ion trap quantum com-
puter; Bell states; entanglement; controlled-NOT gate; state tomography; laser
PACS: 03.67.Lx; 03.67.Mn; 32.80.Pj.
Quantum information processing was proposed and considered ﬁrst by
Feynman and Deutsch.
The requirements for a quantum processor are
nowadays known as the DiVincenzo criteria.
Storing and processing quan-
tum information requires: (i) scalable physical systems with well-deﬁned
qubits; which (ii) can be initialized; and have (iii) long lived quantum states
in order to ensure long coherence times during the computational pro-
cess. The necessity to coherently manipulate the stored quantum informa-
tion requires: (iv) a set of universal gate operations between the qubits
which must be implemented using controllable interactions of the quantum
systems; and ﬁnally, to determine reliably the outcome of a quantum compu-
tation (v) an efﬁcient measurement procedure. In recent years, a large vari-
ety of physical systems have been proposed and investigated for their use in
ur Experimentalphysik, Universit
at Innsbruck, Technikerstrasse 25, A-6020
ur Quantenoptik und Quanteninformation,
Osterreichische Akademie der
Wissenschaften, Technikerstrasse 25, A-6020 Innsbruck, Austria.
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