Research Highlights

Atomic & Molecular Physics | Precision Measurement | Quantum Information Science & Technology
JILA Fellow and NIST Physicist Adam Kaufman Combines Multiple Atomic Clocks into One System
JILA researchers Lukin Yelin and Cao in the Kaufman lab at JILA. (Credit: Patrick Campbell/CU Boulder)
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JILA Fellow and NIST (National Institute of Standards and Technology) Physicist and University of Colorado Boulder Physics professor Adam Kaufman and his team have ventured into the minuscule realms of atoms and electrons. Their research involves creating an advanced optical atomic clock using a lattice of strontium atoms, enhanced by quantum entanglement—a phenomenon that binds the fate of particles together. This ambitious project could revolutionize timekeeping, potentially surpassing the "standard quantum limit" of precision. 

In collaboration with JILA and NIST Fellow Jun Ye, the team highlighted their findings in Nature, demonstrating how their clock, operating under certain conditions, could exceed conventional accuracy benchmarks. Their work advances timekeeping and opens doors to new quantum technologies, such as precise environmental sensors.

PI: Adam Kaufman
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Laser Physics | Precision Measurement | Quantum Information Science & Technology
The Interference of Many Atoms, and a New Approach to Boson Sampling
Atoms in an optical lattice perform a "quantum walk" where they experience many different quantum phenomena, such as superposition or tunneling.
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In daily life, when two objects are “indistinguishable,” it’s due to an imperfect state of knowledge. As a street magician scrambles the cups and balls, you could, in principle, keep track of which ball is which as they are passed between the cups. However, at the smallest scales in nature, even the magician cannot tell one ball from another. True indistinguishability of this type can fundamentally alter how the balls behave. For example, in a classic experiment by Hong, Ou, and Mandel, two identical photons (balls) striking opposite sides of a half-reflective mirror are always found to exit from the same side of the mirror (in the same cup). This results from a special kind of interference, not any interaction between the photons. With more photons, and more mirrors, this interference becomes enormously complicated.

Measuring the pattern of photons that emerges from a given maze of mirrors is known as “boson sampling.” Boson sampling is believed to be infeasible to simulate on a classical computer for more than a few tens of photons. As a result, there has been a significant effort to perform such experiments with actual photons and demonstrate that a quantum device is performing a specific computational task that cannot be performed classically. This effort has culminated in recent claims of quantum advantage using photons.

Now, in a recently published Nature paper, JILA Fellow and NIST Physicist and University of Colorado Boulder Physics Professor Adam Kaufman and his team, along with collaborators at NIST (the National Institute of Standards and Technology), have demonstrated a novel method of boson sampling using ultracold atoms (specifically, bosonic atoms) in a two-dimensional optical lattice of intersecting laser beams. 

PI: Adam Kaufman
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Precision Measurement | Quantum Information Science & Technology
New Spin-Squeezing Techniques Let Atoms Work Together for Better Quantum Measurements
Higher accuracy atomic clocks, such as the “tweezer clock” depicted here, could result from linking or “entangling” atoms in a new way through a method known as “spin squeezing,” in which one property of an atom is measured more precisely than is usually allowed in quantum mechanics by decreasing the precision in which a complementary property is measured.
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Opening new possibilities for quantum sensors, atomic clocks and tests of fundamental physics, JILA researchers have developed new ways of “entangling” or interlinking the properties of large numbers of particles. In the process they have devised ways to measure large groups of atoms more accurately even in disruptive, noisy environments. 

The new techniques are described in a pair of papers published in Nature. JILA is a joint institute of the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder. 

PI: Adam Kaufman | PI: Ana Maria Rey
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Quantum Information Science & Technology
Seeing Quantum Weirdness: Superposition, Entanglement, and Tunneling
Long-lived entangelement of Bell state pairs compared to single unentangled atoms in a 3D optical lattice. The Bell state "stopwatch" ticks twice as fast than that of a single atom, holding the promise of higher stability and higher bandwidth for optical clocks.
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Quantum science promises a range of technological breakthroughs, such as quantum computers that can help discover new pharmaceuticals or quantum sensors for navigation. These capabilities rest on two unusual properties of quantum systems, superposition and entanglement. Just as a computer register stores information in the zeros or ones of classical bits, quantum bits, or qubits, store quantum information—but in the quantum world, superposition allows the qubit to be both a zero and a one at the same time. Furthermore, multiple qubits can be bizarrely correlated through a process called entanglement. When two qubits are entangled with each other, each qubit individually looks to be in a random state, but measuring one qubit reveals perfect information about its entangled partner. These properties of superposition and entanglement make qubits quite special, as they can work more efficiently than a classical computer’s bits.

However, a common challenge in actually using these quantum systems arises due to their limited memory time, or “coherence” time, which is often measured in milliseconds. Many researchers at JILA study and use superposition and entanglement of quantum systems, including JILA fellow Adam Kaufman. Previously, Kaufman and his research team focused on improving the coherence time of the strontium atoms’ superposition between the ground state and the “clock” state, so named because these two states form the basis for state-of-the-art atomic clocks. As reported in two new papers, researchers from this lab have extended these studies to much larger system sizes, with an atom in a superposition of hundreds of locations, and separately, demonstrating optical clock entanglement with seconds-scale coherence time.

PI: Adam Kaufman
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Precision Measurement | Quantum Information Science & Technology
Tweezing a New Kind of Qubit
A rendering of a ytterbium qubit held within a set of optical tweezers
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JILA has a long history in quantum research, advancing the state of the art in the field as its Fellows study various quantum effects. One of these Fellowsis Adam Kaufman. Kaufman and his laboratory team work on quantum systems that are based on neutral atoms, investigating their capacities for quantum information storage and manipulation. The researchers utilize optical tweezers—arrays of highly focused laser beams which hold and move atoms—to study these systems. Optical tweezers allow researchers exquisite, single-particle experimental control. In a new paper published in Physical Review X, Kaufman and his team demonstrate that a specific isotope, ytterbium-171 (171Yb), has the capacity to store quantum information in decoherence-resistant (i.e., stable) nuclear qubits, allows for the ability to quickly manipulate the qubits, and finally, permits the production of such qubits in large, uniformly filled arrays. 

PI: Adam Kaufman
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Atomic & Molecular Physics | Laser Physics | Precision Measurement
Tweezing a New Kind of Atomic Clock
optical tweezers holding atoms, connected by a clock
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Using optical tweezers, the Kaufman and Ye groups at JILA have achieved record coherence times, an important advance for optical clocks and quantum computing.

PI: Adam Kaufman | PI: Jun Ye
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Atomic & Molecular Physics
The Strontium Optical Tweezer
Figure of trapped and cooled single alkaline-earth atoms.
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JILA researchers have, for the first time, trapped a single alkaline-earth atom and cooled it to its ground state. To trap this atom, researchers used an optical tweezer, which is a laser focused to a pinpoint that can hold, move and manipulate atoms. The full motional and electronic control wielded by this tool enables microscopically precise studies of the limiting factors in many of today’s forefront physics experiments, especially quantum information science and metrology. 

PI: Adam Kaufman
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