Simulate the creation of particles in the magnifying universe using quantum computers

A new study published in Scientific Reports simulates particle creation in the expanding universe using an IBM quantum computer and demonstrates digital quantum simulations of quantum field theory in curved space-time (QFTC).

Although attempts to create a perfect quantum theory of gravity have failed, there is another approach to exploring and explaining cosmological events.

QFTC maintains space-time as a classical background described by the general theory of relativity, mechanically dealing with the fields of problems and force within it. This allows physicists to study quantum effects in “curved space-time” without the need for a complete theory of quantum gravity.

This semiclassical theory already predicts phenomena such as Hawking radiation from black holes and the creation of particles in the expansion of space-time. However, these predictions are difficult to test experimentally.

Therefore, scientists have used analog quantum simulations such as Bose-Einstein condensate to verify these phenomena, leaving digital quantum simulations unexplored.

Phys.org spoke to the first author of the study, Marco Díaz Maceda, graduate students at Universidad Autónomade Madrid.

“I think quantum computing has a promising future for researching physics. I’ve always loved studying the universe and its phenomena, so I’m in a quantum field with a naturally curved space-time. This study represents an attractive intersection of these two fields, which is a natural and exciting choice for me,” said Makeda.

Error mitigation and error correction

In the current “noisy mid-scale quantum” (NISQ) era, quantum computers have three main characteristics: This includes noise. That is, Qubits and quantum gates are susceptible to environmental noise, and these devices have almost dozens or hundreds of kits.

These devices are powerful and can be used for applications such as optimization problems and machine learning tasks, but they have major bottlenecks that are hardware.

Quantum Error Correction Codes (QECC) have been shown to work theoretically, but are difficult to implement. Creating a single logic kit requires many physical qubits.

This overhead requirement makes QECC unrealistic to implement on current quantum computers with only tens or hundreds of physical qubits.

In this study, the researchers overcome this by suggesting error mitigation in contrast to error correction. The idea behind this is to understand how system errors scale with noise.

Once understood, researchers can work backwards to estimate error-free results.

Maceda explained the importance of this technology in relation to research. “We only used four qubits per possible state in the field. However, because the circuit contains many quantum gates, errors were accumulated during execution. Reliable results, error mitigation The technique was applied, which increased the fidelity of the calculations.”

Creating particles

QFT assumes a flat space-time known as the “Minkowski Space.” However, if space-time is curved or dynamic (like an expanding universe), physics changes.

When space-time (during inflation) grows or expands, this new space-time excites a vacuum state (or zero-point energy state) leading to the creation of new particles. This particle creation process is believed to have occurred in early universes.

To simulate this process, researchers chose the Friedman-Lemaitre-Robertson-Walker (flrw) universe metric to explain spacetime. This metric explains how space-time expands uniformly and isotropically.

For quantum fields, we explain curved, expanding space-time, considering large scalar fields that evolve according to the modified Klein Gordon equation.

Finally, to illustrate the process of creating the particles, the researchers used the Bogolibov transform. These transformations provide a way for researchers to calculate the number of particles created in space-time, i.e. changes in the initial and final state.

Implementing quantum circuits

Researchers designed quantum circuits that simulate this process using IBM’s 127-kut Eagle processor.

The initial state of the universe was designed to start in a vacuum or “zero point energy” state due to the limitation of one excitation per mode.

Following this, researchers implemented quantum circuits for the particle creation process.

Maceda states that “the first step in designing a quantum circuit was to determine the time evolution operator of the system. This was achieved by associating the initial and final states through the Bogolibov transform,” quantum We explained the process of designing a circuit.

This step allowed us to calculate the number of particles created during the process.

Maceda continues, “After establishing this relationship, we assigned the excited state of the scalar field to a specific qubit in the quantum computer.”

The researchers encoded quantum field states into actual physical qubits, each corresponding to the four excitation levels of the system. This includes ground state, one excitation each of the positive and negative modes, and one for both modes.

“Finally, we apply techniques developed by our mentor Dr. Sabin to map temporal evolution operators to a single operation acting on these Qubits, and accurately apply the dynamics of the scalar fields of the universe, where their evolution expands. We guaranteed that it was reflecting,” Maceda said.

To achieve mapping to a single operator capable of acting on the Qubits of time evolution operators, researchers used hundreds of quantum gates.

To mitigate errors, researchers applied “Zero Nooes Extrapolation” (ZNE). This method works by deliberately adding noise to the system in a controlled way, measuring how the noise affects the outcome, and moving backwards to a zero noise state.

A viable tool for future research

The simulations were successful in creating particles in the expansion of space-time, and agreed that the results matched theoretical predictions. Quantum computer results showed higher noise, but feasibility was shown.

Furthermore, ZNE technology significantly improves results, indicating the possibility of using quantum simulations to study complex systems.

Describing the influence of their work on cosmology, Makeda explains, “Our work offers a new way to simulate particle creation in the early universe, and deeper insights into the fundamental processes that shape the universe. “We provide the following.”

Researchers also believe that digital quantum simulation is becoming a pre-existing state, and it continues to become a viable tool for investigating cosmological phenomena.

“Digital quantum simulations have already been used by our mentor Dr. Sabin, and are studying topics such as the intertwining of gravity, the Lindler transformation explaining the evaporation of black holes, and the causal structure of the universe,” commented Makeda. Masu.

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