^newsbreaks
3R optical regenerator
improves bit-error ratio

Researchers at the University of Sydney (Sydney,

Australia) have demonstrated a reamplification, re-

shaping, and retiming (3R) optical regenerator archi-

tecture that can improve the bit-error ratio (BER) of

a signal passing through it. Typical 2R (reamplifying

and reshaping)) and 3R regenerators provide output

power based only on instantaneous input power; a

noisy input signal exits such regenerators with a BER

that is degraded or at best identical to the input BER.

The Australian researchers present a 2R and

a 3R regeneration architecture that improves BER

based on the principle of nonlinear spectral broaden-

ing (for 2R) or nonlinear spectral shifting (for 3R), fol-

lowed by filtering, experimentally showing that the 3R

regenerator discriminates pulses of different widths

by assigning them different power transfer func-

tions. With their 3R architecture, they demonstrated

BER improvement of a noisy signal by four orders of magnitude, from 3 × 10^{– 6} without the regenerator to 2 × 10^{– 10}, and expect further BER improvement

with optimization of regenerator parameters. Contact

Martin Rochette at rochette@physics.usyd.edu.au or

rochette@photonics.ece.mcgill.ca.

Ion trap may eventually
enable mass production of
quantum computers

Researchers at the National Institute of Standards and

Technology (NIST; Boulder, CO) have designed and built

an electromagnetic trap for ions that could potentially

be mass-produced to make quantum computers large

enough for practical use. It is the first functional ion trap in

which all electrodes are arranged in a single-layer “chiplike”

geometry, which should be much easier to manufacture

than previous ion traps with multiple electrode layers.

The structure, fabricated using standard photolithogra-

phy and metal-deposition techniques, consists of a polished

fused-quartz substrate, coated first with a titanium adhesion

layer and then with a copper seed layer. Resistors and leads

were patterned onto the structure using photolithography,

and it was electroplated with gold electrodes. Ions were cre-

ated in the completed trap by photoionizing thermally evapo-

rated neutral magnesium atoms, and individual laser-cooled

magnesium ions were confined in the linear Paul trap about

40 µm above the electrode plane. The NIST scientists report-

ed a heating rate in the device of about 5 motional quanta

per millisecond for a trap frequency of 2. 83 MHz, sufficiently

low to be useful for quantum information processing. Con-

tact David Wineland at david.wineland@nist.gov.

Dual-color superlattice thermal imager remotely senses carbon dioxide

Bispectral mid-IR imaging detectors have capabilities that single-color ver-

sions don’t, including absolute remote temperature measurement and a height-

ened ability to pick objects out from cluttered backgrounds based on spectral

signatures. Researchers at the Fraunhofer-Institut für Angewandte Festkörper-

physik (Freiburg, Germany) have developed a dual-color thermal superlattice

focal-plane array (FPA) based on indium arsenide/gallium antimonide, which is

less expensive than the mercury cadmium telluride used in prevalent devices.

The device is especially well suited for remote imaging of carbon dioxide,

which emits strongly at 4. 2 µm.

The 288 × 384-pixel FPAs are lithographically fabricated in batches of four

on full wafers. Each FPA is 16. 1 × 12. 1 mm in size and is flip-chip hybridized to a silicon readout integrated circuit, which supports snapshot integration and individual control of bias for both colors. The 50%-cutoff wavelengths for the

two (“blue” and “red”) channels are 4.0 and 5.0 µm at 77 K. The FPA is cooled by a Sterling cooler. The blue and red

channels a noise-equivalent temperature difference of 29 and 16. 5 mK, respectively. The carbon dioxide signature is