to develop quantum-logic
components and quantum
information systems based on
trapped ions, in support of
new atomic frequency standards
and a national program
aimed at advancing computation
and communication.
INTENDED OUTCOME AND
BACKGROUND
We conduct research on the development
and properties of prototype quantum-
logic devices consisting of small
numbers of electromagnetically trapped
and laser-cooled ions serving as quantum
bits (qubits). This research comprises
quantum computing, quantum
measurement (including noise reduction
in frequency standards), and development
of new classes of quantum-logicbased
frequency standards.
This project arose as part of a long-term
research program on ion-based frequency
standards. In particular, the goal of
reducing fundamental quantum projection
noise suggested the possibility of
using similar approaches for quantum
computing and quantum metrology.
Division researchers soon became leaders
in quantum computing research, and
NIST-wide programs in quantum computing
and quantum communications
rapidly developed and demonstrated
significant success.
Our focus on quantum computing
meets two primary needs. First, quantum
computing research is a national
priority to ensure economic and physical
security, with substantial investment
by both defense and civilian funding
agencies. Our unique expertise in quantum
state engineering has made the
trapped-ion quantum computing program
a world-leading effort.
But the Division work on quantum
state engineering also directly serves our
time and frequency metrology mission.
For example, we recently demonstrated
Heisenberg-limited spectroscopy with
three entangled ions, in a scheme that
could be scaled to an arbitrary number
of ions or atoms. In principle, this could
dramatically reduce the averaging time
required for a frequency standard to
reach its statistical uncertainty limit,
substantially improving the performance,
and broadening the applications,
of atomic clocks.
Accomplishments
Progress in Quantum State
Manipulation for Quantum
Computing and Quantum
Measurement
Figure 7. David Wineland adjusting one of the systems used for studying quantum-logic gates. |
The Division's quantum computing and quantum measurement program continues
to make strong progress.
Division researchers demonstrated the
ability to sympathetically laser-cool ions
of different species in a trap. In one
experiment, a two-ion crystal consisting
of a 9Be+ ion and a
24Mg+ ion was
cooled by laser irradiation on only one
ion. The laser-cooled "refrigerant" ion
sympathetically cooled the other ion
through the Coulomb interaction, but
because transitions in the two ions were
separated by some 30 nm in wavelength,
irradiation of one ion had no direct effect on the other.
This property enables an entangled pair
of ions of different species to be laser
cooled without perturbing the qubit
information. Such a process could be
very useful in a complex, multi-ion
quantum computing architecture, where
motional heating from quantum state
manipulations must be removed without perturbing qubit states.
Sympathetic cooling also broadens the
range of ions that can be used as potential
frequency standards. For example,
27Al+ has potentially good clock transitions
but no easily accessible laser cooling
transitions. The Division is investigating
the potential of a 27Al+ frequency
standard using 9Be+ sympathetic cooling
and entangled state spectroscopy.
Division researchers have conducted
many experiments demonstrating the
effectiveness of various logic gates and
demonstrating quantum computing
architectures that are, in principle, completely
scalable--based on ions manipulated
by lasers and multi-zone traps.
Division researchers also demonstrated a
robust, high-fidelity logic gate based
only on changes of phase in a two-ion
9Be+ system. (See Fig. 7.)
Recently, Division researchers demonstrated
deterministic quantum teleportation
of qubits in a three-ion trap. A
coherent superposition of two internal
states was generated in one of the ions,
and then the quantum states were teleported
to a second ion through a third,
intermediary ion. This experiment and a
similar one simultaneously reported by a
group from Innsbruck were the world's
first demonstrations of teleportation of
massive particle qubits, rather than photon
qubits. Quantum teleportation
could be crucial to realization of a largescale
quantum computer, enabling rapid
transmission of qubit information
throughout the computer without the
need to physically move qubits.
First strategic focus |
Second strategic focus |
Third strategic focus |
Fourth strategic focus
"Technical Activities 2004" - Table of Contents |
