#stringbreaking

Scientists improved particle physics simulation by utilising quantum computers to simulate and watch “string breaking” in real time. Traditional computers couldn't replicate this complicated process, in which subatomic particles like quarks are joined by "strings" of force fields that release energy when they break.

The groundbreaking findings are the latest step towards using quantum computers for simulations that surpass conventional machines. These quantum simulations are “incredibly encouraging,” says LBNL scientist Christian Bauer. He said “string breaking is a very important process that is not yet fully understood from first principles”. Classical computers can calculate the ultimate effects of particle collisions involving string generation or breaking, but not the intermediate dynamics.

Two Simulation Methods Revealed

Two worldwide academic-business research teams conducted the experiments. Two teams worked at theGoogle Quantum AI Lab in Santa Barbara, California, and Cambridge startup QuEra Computing. These groups discovered string breaking employing “diametrically opposite quantum-simulation philosophies”:

Analogue Quantum Simulation (QuEra Computing):

This team included Harvard, Innsbruck, and QuEra Computing researchers using QuEra's Aquila computer.

The data was encoded in rubidium atoms kept in place by optical “tweezers” in a 2D honeycomb or kagome-geometry pattern.

The electric field at a given position in space was reflected by each atom's qubit, which could be stimulated or relaxed.

This analogue quantum simulation relied on arranging the atoms so that their electrostatic forces mimicked the electric field. This arrangement allowed the system to continuously attain lower energy levels.

This technology allowed the first observation of string breaking in a programmable two-dimensional quantum simulator. The “tabletop analogue of quark confinement,” a key property of QCD, was achieved.

◦ Daniel González-Cuadra, co-author of the QuEra paper and theoretical physicist and assistant professor at the Institute for Theoretical Physics (IFT) in Madrid, said neutral-atom devices can now solve theoretical difficulties. He said “seeing string breaking in a controlled 2D environment marks a critical step towards using quantum simulators to explore high-energy physics”.

Alexei Bylinskii, QuEra's VP of Quantum Computing Services, said this alliance “underscores the value of open, programmable neutral-atom hardware for fundamental research.” Research in condensed-matter, high-energy, and quantum-information science is enhanced by flexible access to Aquila's multi-qubit capabilities.

Professor Peter Zoller, a senior author at IQOQI and the University of Innsbruck and “founding father of modern quantum simulation,” said “Gauge theories govern much of modern physics.” By showing non-abelian gauge fields and topological matter in two dimensions where strings can bend and fluctuate, the basis is established for studying them.

The experiment featured dynamic quenches using local detuning ‘kicks’ to watch strings snap and re-form in real time, revealing resonance peaks signalling many-body tunnelling processes; programmable geometry, where atoms were placed on hexagonal lattice links to enforce Gauss's-law constraints via Rydberg blockade; and tuneable string tension by varying laser detuning and interaction radius. This work stretched one-dimensional demonstrations to two spatial dimensions, when theoretical and numerical techniques near saturation.

Google Quantum AI Lab (Digital Quantum Simulation) utilised the Sycamore processor.

The chip's superconducting loop states encoded the 2D quantum field, unlike the analogue method.

This “digital” quantum simulator delicately controls the quantum field's evolution “by hand” using discrete manipulations.

Frank Pollmann, a physicist from the Technical University of Munich (TUM) in Garching, Germany, who led the Google experiment, said both teams placed strings in the field that “effectively acted like rubber bands connecting two particles.” Researchers adjusted settings to make strings stiff, wobbly, or breakable. Pollmann sometimes said, “The whole string just dissolves: the particles become deconfined.”

Importance and Future

These experiments are necessary to employ quantum computers for simulations beyond regular machines. The results demonstrate the scalability of neutral-atom platforms like Aquila for simulating complex quantum field theories and set a benchmark for quantum simulation by pushing classical computational capabilities in real-time gauge-theory dynamics. This confirms the growing importance of quantum hardware for scientific study.

Simulating strings in a 2D electric field can be useful in material physics, but high-energy interactions like those in particle colliders, which require the stronger nuclear force, are difficult to replicate. Monika Aidelsburger, a physicist at Munich's Max Planck Institute of Quantum Optics, says these more complex simulations have “no clear path at this point how to get there”.

She added that quantum simulation has advanced “really amazing and very fast” overall. Because ‘qudits’ quantum systems with more than two quantum states may produce more accurate representations of a quantum field and enhance simulation power, researchers are considering using them. Christian Bauer and LBNL colleague Anthony Ciavarella were among the first to model the strong nuclear force with a quantum computer last year.

This research will boost particle physics and demonstrate quantum computing's scientific discovery potential.

Financial Support and Recognition

Quantum Simulator

A multinational team of researchers reported the first direct detection of “string breaking” in a programmable two-dimensional quantum simulator, advancing fundamental physics. This landmark Nature article from June 4, 2025, pushes computer power limits and opens new avenues for high-energy physics research.

QuEra Computing, Harvard University, and the University of Innsbruck scientists demonstrated real-time gauge-theory dynamics that were previously thought impossible.

Deciphering String Breaking

String breaking is fundamental to lattice gauge theories (LGTs), which explain many particle and condensed matter physics events. Well-known examples include contention, which keeps quarks like protons and neutrons inside hadrons. The “string” of gluon fields connecting a quark and an antiquark stores energy that grows linearly with their separation. When this energy generates new quark-antiquark pairs from the vacuum, the original string will “snap” or “break”.

The extreme conditions needed to empirically see this phenomenon in nature make it difficult. This new study gives a tabletop analogue of this basic component of the strong nuclear force, providing a new insight.

Simulating Strong Force using Atoms

Researchers used QuEra's Aquila neutral-atom platform to assemble several dozen rubidium atoms in a Kagome-shaped optical-tweezer lattice. This configuration is crucial because it closely mimics the strong nuclear force mathematical model and naturally provides a constraining lattice-gauge theory.

This simulation heavily uses Rydberg obstruction. Rydberg atoms "block" each other, thus only one can be excited at a time due to van der Waals interactions. This action naturally produces a linear confinement potential and a local U(1) symmetry for two synthetic charges, allowing researchers to precisely tune their string tension and masses.

Considered the lowest circumstances needed to identify this event. Profited from neutral atom simulator experimental control advances, noted Peter Zoller teammate Torsten Zache.

Experimental Prowess: Equilibrium to Dynamics

They performed several complex checks to see if the string broke:

Equilibrium: Flaws were evident when the atom array's ground state was prepared adiabatically. Because of this, they could distinguish restricted phase zones with broken string configurations from those dominated by fluctuating strings. The probability of broken and unbroken string states were compared to global detuning and Rydberg blockade radius.

Dynamic Quenches: Local control lets them “quench” string states from atomic detuning to study string breaking dynamics in real time. These nanosecond dynamics showed a fascinating many-body resonance phenomenon. The strings broke and reformed due to local detuning “kicks,” revealing resonance peaks that suggest many-body tunnelling. Different string configurations were quenched to various local detuning values and monitored for time-evolved probability.

It expands on past one-dimensional demonstrations to two spatial dimensions, which is fast saturated for theoretical and numerical approaches.

Why This Matters: Physics' Quantum Leap

This firsthand finding of string breaking in a 2D quantum simulator affects many scientific fields:

The ability to model real-time gauge-theory dynamics with dozens of qubits supports quantum technology as a powerful discovery tool by pushing classical simulations to their limits. First author Dr. Daniel González-Cuadra, an assistant professor at the Institute for Theoretical Physics (IFT) in Madrid, said observing string breaking in a controlled 2D environment is vital to exploring high-energy physics utilising quantum simulations. It shows how neutral-atom devices can solve theoretical problems.

Bridge to Particle Physics: Quark confinement breaks strings in quantum chromodynamics (QCD). The fresh insights these tabletop experiments provide into the fundamental forces regulating the universe may help future lattice-QCD and collider research.

Scalable Neutral-Atom Platform: Controlled gauge-theory dynamics in two spatial dimensions utilising dozens of qubits show the adaptability and scalability of neutral-atom arrays like Aquila. This piece shows their ability to handle more complex many-body situations. “This collaboration highlights the importance of open, programmable neutral-atom hardware for fundamental research,” said QuEra VP of Quantum Computing Services Alexei Bylinskii, a key author. Researchers can use Aquila's multi-qubit capabilities to accelerate quantum-information science, high-energy, and condensed-matter discoveries.

Foundation for Future Discoveries: Professor Peter Zoller, a senior author and quantum simulator pioneer, stressed the relevance of two-dimensionality, “Gauge theories govern much of modern physics.” This prepared for future discoveries. It lays the groundwork for investigating non-abelian gauge fields and topological matter in two dimensions with strings that bend.