The building elements of quantum computers, qubits, can be manufactured using a variety of technologies. One option to generate a qubit is to employ a concentrated laser to trap a single neutral atom in situ, a technique that won the Nobel Prize in 2018.
However, many individual atoms must be kept in place by multiple laser beams in order to build a quantum computer out of neutral atom qubits. Because creating an array out of two elements would be prohibitively difficult, these arrays have only been formed from atoms of a single element thus far.
However, University of Chicago researchers have built a hybrid array of neutral atoms from two separate elements for the first time, considerably expanding the system’s quantum technology capabilities. The findings were reported in Physical Review X, with funding from the NSF Quantum Leap Challenge Institute Hybrid Quantum Architectures and Networks (HQAN).
Hannes Bernien, the project’s principal researcher and an assistant professor at the University of Chicago’s Pritzker School of Molecular Engineering, said, “There have been many examples of quantum technology that have taken a hybrid approach.” “However, for these neutral atom platforms, they have yet to be developed.” We’re ecstatic to see that our findings have elicited such a good response from the public, and that new protocols based on our hybrid methodologies are in the works.”
Double the potential
While man-made qubits like superconducting circuits require quality control to remain absolutely consistent, neutral atoms created from a single element all have the same properties, making them great candidates for qubits.
However, because every atom in the array has the same properties, measuring a single atom without disrupting its neighbors is incredibly difficult—they’re all on the same frequency, so to speak.
“Over the last few years, there have been a number of landmark experiments demonstrating that atomic array platforms are extremely well suited for quantum simulation and quantum computation,” Bernien said. “However, because all the atoms have the same resonances, measurements on these systems tend to be destructive.” In this situation, this novel hybrid technique could be extremely beneficial.”
Any atom’s nearest neighbors in a hybrid array consisting of atoms of two different elements can be atoms of the other element, with radically different frequencies. Researchers will be able to measure and manage a single atom without interference from the atoms around it much easier as a result of this.
It also allows researchers to avoid a common issue with atomic arrays: keeping an atom in one position for an extended period of time.
“When you do these experiments with single atoms, you lose the atoms at some point,” Bernien explained. “And then you have to re-initialize your system by first creating a new, cold cloud of atoms and then waiting for individual ones to be trapped by the lasers once more.” However, because of the hybrid design, we may conduct separate tests with these species. We can conduct an experiment with atoms of one element while refreshing the other atoms, then swap to ensure that qubits are always available.”
Making a bigger quantum computer
Bernien’s team built a hybrid array of 512 lasers: 256 with cesium atoms and 256 with rubidium atoms. This is a lot of qubits in terms of quantum computers: Google and IBM’s quantum computers, which are comprised of superconducting circuits rather than trapped atoms, have only reached about 130 qubits. Despite the fact that Bernien’s gadget is not yet a quantum computer, quantum computers created from atomic arrays are considerably easier to scale up, which could lead to some significant new discoveries.
“We don’t know what happens when you scale up a very coherent system that can isolate itself from the environment,” Bernien explained. “This trapped atom approach has the potential to be a fantastic tool for investigating large-system quantum effects in previously unknown regimes.”
The array’s hybrid nature also allows for a variety of applications that would not be viable with a single atom species. Because the two species are independently programmable, the atoms of one may be utilized as quantum memory while the atoms of the other can be used to do quantum computations, thereby replacing the RAM and CPU in a traditional computer.
Bernien stated, “Our work has already inspired theoreticians to think about new protocols for it, which is exactly what I hoped.” “I hope it inspires people to consider how these tools can be used for state control and measurements.” We’ve already seen some really great protocols that we’d like to put in place on these arrays.”