Princeton University physicists, including Lawrence Cheuk and Connor Holland, have successfully linked individual molecules into quantum mechanically “entangled” states for the first time. This breakthrough could pave the way for quantum computers, simulators, and sensors that outperform their traditional counterparts. The team overcame the challenge of controlling molecules by using a complex system of tightly focused laser beams, or “optical tweezers”. The research, which was published in the journal Science, was also independently verified by a team from Harvard University and the Massachusetts Institute of Technology.
Quantum Entanglement of Molecules Achieved by Physicists
For the first time, physicists from Princeton University have successfully entangled individual molecules in a quantum state. This means that the molecules remain correlated and can interact simultaneously, regardless of the distance between them. This research, which marks a significant breakthrough in quantum physics, was published in the journal Science.
Quantum entanglement is a fundamental concept in quantum mechanics, where two particles become inextricably linked with each other, maintaining this link even if they are light years apart. This phenomenon, once described by Albert Einstein as “spooky action at a distance,” has been proven to be an accurate description of the physical world. Those who might want to understand more, may want to look at the Bell Inequality and the man behind the Bell Inequality, John Bell.
The successful entanglement of molecules is a theoretical breakthrough and has practical implications. Entangled molecules can be the building blocks for many future applications, including quantum computers, quantum simulators, and quantum sensors.
Quantum Advantage and the Challenge of Controllable Quantum Entanglement
The ability of quantum devices to outperform classical ones is known as “quantum advantage.” This advantage is primarily due to the principles of superposition and quantum entanglement. Unlike classical computer bits that can assume the value of either 0 or 1, quantum bits, or qubits, can simultaneously be in a superposition of 0 and 1.
However, achieving controllable quantum entanglement and building quantum advantage remains a challenge. Scientists and engineers are still exploring the best physical platform for creating qubits. Various technologies, such as trapped ions, photons, and superconducting circuits, have been explored as potential platforms for quantum computers and devices.
The Role of Molecules in Quantum Entanglement
Until this experiment, molecules had long defied controllable quantum entanglement. However, the Princeton team found a way to control individual molecules and coax them into these interlocking quantum states. They believe that molecules have certain advantages over atoms, making them particularly suitable for certain applications in quantum information processing and quantum simulation of complex materials.
Molecules have more quantum degrees of freedom and can interact in new ways compared to atoms. This means that there are new ways of storing and processing quantum information. However, the complexity of molecules makes them notoriously difficult to control in laboratory settings.
The Experiment: Achieving Quantum Entanglement of Molecules
The team addressed these challenges through a carefully designed experiment. They first selected a molecular species that is both polar and can be cooled with lasers. The molecules were then cooled to ultracold temperatures where quantum mechanics takes center stage. Individual molecules were picked up by a complex system of tightly focused laser beams, known as “optical tweezers.”
The researchers were able to create large arrays of single molecules and individually position them into any desired one-dimensional configuration. They then encoded a qubit into a non-rotating and rotating state of the molecule, demonstrating the ability to create well-controlled and coherent qubits out of individually controlled molecules.
The Potential of Molecular Quantum Entanglement
The potential of this research for investigating different areas of quantum science is significant, given the innovative features offered by this new platform of molecular tweezer arrays. The team is particularly interested in exploring the physics of many interacting molecules, which can be used to simulate quantum many-body systems where interesting emergent behavior such as novel forms of magnetism can appear.
The research, “On-Demand Entanglement of Molecules in a Reconfigurable Optical Tweezer Array,” was published in Science, on December 8, 2023. The work was supported by Princeton University, the National Science Foundation, and the Sloan Foundation.
“This is a breakthrough in the world of molecules because of the fundamental importance of quantum entanglement,” said Lawrence Cheuk, assistant professor of physics at Princeton University and the senior author of the paper. “But it is also a breakthrough for practical applications because entangled molecules can be the building blocks for many future applications.”
“One of the motivations in doing quantum science is that in the practical world it turns out that if you harness the laws of quantum mechanics, you can do a lot better in many areas,” said Connor Holland, a graduate student in the physics department and a co-author on the work.
“Quantum entanglement is a fundamental concept,” said Cheuk, “but it is also the key ingredient that bestows quantum advantage.”
“What this means, in practical terms, is that there are new ways of storing and processing quantum information,” said Yukai Lu, a graduate student in electrical and computer engineering and a co-author of the paper. “For example, a molecule can vibrate and rotate in multiple modes. So, you can use two of these modes to encode a qubit. If the molecular species is polar, two molecules can interact even when spatially separated.”
“Using molecules for quantum science is a new frontier and our demonstration of on-demand entanglement is a key step in demonstrating that molecules can be used as a viable platform for quantum science,” said Cheuk.
“The fact that they got the same results verify the reliability of our results,” Cheuk said. “They also show that molecular tweezer arrays are becoming an exciting new platform for quantum science.”
Summary
For the first time, physicists at Princeton University have successfully linked individual molecules into quantum mechanically “entangled” states, where the molecules remain interconnected even when separated by vast distances. This breakthrough could pave the way for practical applications such as quantum computers, simulators and sensors that outperform their traditional counterparts, thanks to the principles of superposition and quantum entanglement.
- A team of physicists from Princeton University, including Lawrence Cheuk and Connor Holland, have successfully linked individual molecules into quantum mechanically “entangled” states for the first time.
- Quantum entanglement is a state where molecules remain correlated and can interact simultaneously, regardless of the distance between them.
- This breakthrough could have practical applications, including the development of quantum computers, simulators, and sensors that outperform their traditional counterparts.
- Quantum advantage, the ability of quantum devices to outperform classical ones, is based on principles of superposition and quantum entanglement.
- The team managed to control individual molecules and coax them into these interlocking quantum states, overcoming previous challenges due to the complexity of molecules.
- The researchers used a series of microwave pulses to make individual molecules interact with one another in a coherent fashion, implementing a two-qubit gate that entangled two molecules.
- This research opens up new possibilities for investigating different areas of quantum science, particularly the physics of many interacting molecules.
- A separate research group led by John Doyle and Kang-Kuen Ni at Harvard University and Wolfgang Ketterle at the Massachusetts Institute of Technology achieved similar results, verifying the reliability of the Princeton team’s findings.
- The study was published in the journal Science and was supported by Princeton University, the National Science Foundation, and the Sloan Foundation.