Researchers used quantum simulations to model the collisions of subatomic particles and open new avenues to understand the basics of hadron collisions, a key aspect of high-energy physics.
The results illustrate quantum computing's potential to expand the range of solutions to scientific problems beyond those made possible by classical high-performance computers.
The study relied on support from the Quantum Computing User Program (QCUP) and the Quantum Science Center , a National Quantum Information Science Research Center, at the Department of Energy's Oak Ridge National Laboratory.
The research team, led by senior author Martin Savage, a professor of physics at the University of Washington , employed quantum circuits to simulate hadron collisions. Hadrons are subatomic particles composed of quarks and gluons - two types of smaller, indivisible subatomic particles commonly described as the building blocks of matter. The most familiar hadrons are the protons and neutrons found in an atom's nucleus.
When hadrons collide, the reaction produces huge concentrations of energy and releases a blizzard of particles, all with various energies and compositions.
"These collisions are absolutely essential for a deeper understanding of high-energy physics and the study of matter in extreme conditions, but the size of the necessary equations for modeling them has always been far beyond the capabilities of current classical computers," Savage said. "Now that quantum devices are available that offer hundreds of qubits for simulation, we wanted to see what could be done with this new set of tools."
Classical computers store information in bits equal to either 0 or 1. That means a classical bit, like a light switch, exists in one of two states: on or off.
Quantum computing relies on quantum bits, or qubits, to store information. Qubits, unlike the binary bits used in classical computing, can exist simultaneously in more than one state via quantum superposition, which allows combinations of physical values to be encoded on a single object. That difference allows for a wider range of possible values that could make qubits a viable alternative for tackling problems that have been intractable on classical computers.
Savage and the research team obtained an allocation of time on IBM's Torino quantum computer via QCUP, part of the Oak Ridge Leadership Computing Facility (OLCF), which awards time on cloud-based commercial quantum processors around the country to support research projects. The Torino computer uses superconductors as qubits, one of several quantum computing approaches.
The team first prepared a 1D quantum ground state, or state with the lowest possible energy. The team then used 112 of Torino's 133 qubits to simulate a quantized wave packet, or burst of energy, and evolved the packet forward in time to model the events of a hadron collision, ultimately employing 3,858 two-qubit gates. This approach allowed the team to track how the burst of energy evolved over time through the collision.
The results showed signatures of hadron propagation, or the movement of quarks and gluons observed during a collision. Those results compared favorably to the results achieved via classical numeric simulations, the authors wrote.
Current quantum systems tend to display high error rates, or noise, due to measurement errors, qubit degradation and other causes. The research team used IBM's error-mitigation and uncertainty-quantification techniques to reduce noise and track any deviations from expected results.
The team hopes in future studies to evolve those initial states on quantum hardware, even with few qubits and high error rates. Error-correcting techniques on future quantum computers with many qubits could ultimately achieve greater accuracy than what's currently possible on classical computers, Savage said.
"Such simulations could provide first glimpses … that are beyond present capabilities of classical computing," the authors wrote in the study.
Besides Savage, the research team included Roland Farrell, Marc Illa and Anthony Ciavarella of the InQubator for Quantum Simulation .
Support for this research came from the DOE Office of Science's Advanced Scientific Computing Research program, the DOE Quantum Science Center and the DOE Nuclear Physics InQubator for Quantum Simulation. The OLCF is a DOE Office of Science user facility at ORNL.
UT-Battelle manages ORNL for DOE's Office of Science, the single largest supporter of basic research in the physical sciences in the United States. DOE's Office of Science is working to address some of the most pressing challenges of our time. For more information, visit https://energy.gov/science .
