Fast, Low-Loss Imaging Enables Scalable Quantum Computing with Individual Atoms.

The pursuit of scalable quantum technologies and precision simulation relies heavily on the ability to precisely control and observe individual atoms, a task complicated by the need for rapid, high-fidelity imaging without compromising atomic integrity. Researchers are continually seeking methods to overcome limitations imposed by conventional detection techniques, which often necessitate continuous cooling and lengthy imaging cycles. A team led by R. Klemt, R. Panza, A. Muzi Falconi, S. Sbernardori, R. Forti, F. Scazza, O. Abdel Karim, and M. Marinelli, affiliated with the University of Trieste and Elettra Sincrotrone Trieste, present a novel approach to single-atom imaging in optical tweezers, detailed in their article, “Microsecond-scale high-survival and number-resolved detection of ytterbium atom arrays”. Their work demonstrates a method for fast, low-loss imaging of ytterbium atoms, achieving discrimination fidelities exceeding 99.9% and survival probabilities above 99.5% on microsecond timescales, and importantly, allows for the detection of multiple atoms per site.

Researchers report a method for rapidly and accurately imaging individual ytterbium atoms held in optical tweezers, achieving single-atom discrimination fidelities exceeding 99.9% and retaining over 99.5% of atoms throughout repeated imaging cycles. This system operates without the need for continuous cooling, a notable improvement over conventional fluorescence detection techniques, and facilitates faster experimental iterations with potential applications in quantum computing and precision measurement.

The study establishes a clear distinction in the relative ease of differentiating between varying atom numbers given an illumination time of 1.5 milliseconds. Reliably distinguishing between an empty site and one containing a single atom proves particularly challenging, with likelihood ratios approaching unity, indicating a near-equal probability of either interpretation. However, the research demonstrates a robust ability to differentiate between a site containing one atom and a site containing two or more, achieving significantly higher likelihood ratios and highlighting the system’s sensitivity to higher atom numbers. This capability stems from the imaging scheme’s ability to avoid ‘parity projection’, a phenomenon where the observed signal obscures the true atom number in multiply-occupied traps, allowing for precise atom counting. Parity projection arises from the indistinguishability of identical particles, leading to interference effects that can mask the actual number of atoms present.

Crucially, the method incorporates interleaved recooling pulses, lasting only a few hundred microseconds, to maintain high atom retention rates during repeated imaging cycles, enabling tens of consecutive detections without compromising the number of atoms available for subsequent operations. This feature is vital for building practical quantum processors and atomic clocks, both of which demand repeated measurements and manipulations of individual atoms.

The near-diffraction-limited spatial resolution of this low-loss imaging technique facilitates number-resolved microscopy even in dense atomic arrays, opening avenues for direct site-occupancy readout in optical lattices and enabling precise measurements of density fluctuations and correlations. Optical lattices are created by interfering laser beams, forming a periodic potential that traps atoms. These measurements are essential for simulating complex quantum systems, allowing researchers to probe the behaviour of many-body quantum phenomena and develop new quantum algorithms.

Researchers demonstrate single-atom imaging without continuous cooling, achieving detection fidelities exceeding 99.9% while maintaining a single-shot atom survival probability above 95%. The team utilises ytterbium atoms, leveraging their favourable fluorescent properties to overcome challenges associated with traditional fluorescence imaging and enable faster experimental cycles, paving the way for more efficient and scalable quantum technologies.

Optical tweezers use highly focused laser beams to trap and manipulate microscopic objects, including individual atoms, providing a versatile platform for quantum control. Researchers successfully demonstrate the near-deterministic preparation of single atoms in optical tweezers, driven by collisions assisted by blue-detuned light, enabling precise control over atom placement. Blue-detuned light refers to light with a frequency slightly higher than the atomic resonance frequency, which creates a potential that attracts atoms towards the light source.