A team led by the U.S. Department of Energy’s Argonne National Laboratory, including Professor Dafei Jin from the University of Notre Dame, has made a significant advancement in quantum computing. They have extended the coherence time of their novel type of qubit, known as charge qubits, to 0.1 milliseconds, nearly a thousand times better than the previous record. This allows for many thousands of operations to be performed in a short time. The team’s qubits are single electrons trapped on a solid-neon surface, which resists environmental disturbance. The research, funded by various institutions, was published in Nature Physics.
Quantum Computing: Enhancing Qubit Coherence Time
Quantum computing, with its potential to solve complex problems in climate prediction, material design, and drug discovery, relies on quantum bits or qubits. A team from the U.S. Department of Energy’s Argonne National Laboratory has made significant progress in this field by extending the coherence time of a novel type of qubit to 0.1 milliseconds. This is nearly a thousand times better than the previous record.
In the quantum world, 0.1 milliseconds is a substantial window for a qubit to perform thousands of operations. Unlike classical bits, qubits can exist in both states, 0 and 1, simultaneously. For a qubit to function effectively, it must maintain this mixed state for a sufficiently long coherence time, while also resisting disruptive noise from the surrounding environment.
The team’s qubits, known as charge qubits, encode quantum information in the electron’s motional states. Charge qubits are particularly appealing due to their simplicity in fabrication and operation, and their compatibility with existing infrastructures for classical computers. This simplicity could potentially result in lower costs for building and operating large-scale quantum computers.
The Role of Neon in Qubit Stability
The team’s qubit is a single electron trapped on an ultraclean solid-neon surface in a vacuum. Neon is crucial as it resists disturbance from the surrounding environment. As one of the few elements that do not react with other elements, neon provides a stable platform that protects the electron qubit and inherently guarantees a long coherence time.
The small footprint of single electrons on solid neon means that qubits made with them are more compact and promising for scaling up to multiple linked qubits. Following continued experimental optimisation, the team improved the quality of the neon surface and significantly reduced disruptive signals, resulting in a coherence time of 0.1 milliseconds, a thousand-fold increase from the initial 0.1 microseconds.
The Future of Quantum Computing: Scalability and Entanglement
Scalability, or the ability to link a qubit with many other qubits, is another crucial attribute of a qubit. The team demonstrated that two-electron qubits can couple to the same superconducting circuit, allowing information to be transferred between them through the circuit. This achievement marks a significant step towards two-qubit entanglement, a critical aspect of quantum computing.
The team plans to continue working on extending the coherence time even further and entangling two or more qubits. This research, funded by various institutions including the DOE Office of Basic Energy Sciences and the Julian Schwinger Foundation for Physics Research, was published in Nature Physics.
Collaborating Institutions and Contributors
The research involved several institutions, including Lawrence Berkeley National Laboratory, Massachusetts Institute of Technology, Northeastern University, Stanford University, the University of Chicago, and the University of Notre Dame. Key contributors include Dafei Jin, a professor at the University of Notre Dame with a joint appointment at Argonne, Xu Han, an assistant scientist in CNM with a joint appointment at the Pritzker School of Molecular Engineering at the University of Chicago, and Xinhao Li, a postdoctoral appointee at Argonne.
“Rather than 10 to 100 operations over the coherence times of conventional electron charge qubits, our qubits can perform 10,000 with very high precision and speed.”
— Dafei Jin, professor at the University of Notre Dame with a joint appointment at Argonne’s Center for Nanoscale Materials.
“Among various existing qubits, electron charge qubits are especially attractive because of their simplicity in fabrication and operation, as well as compatibility with existing infrastructures for classical computers,” said Dafei Jin. “This simplicity should translate into low cost in building and running large-scale quantum computers.”
“Thanks to the small footprint of single electrons on solid neon, qubits made with them are more compact and promising for scaling up to multiple linked qubits,” said Xu Han, an assistant scientist in CNM with a joint appointment at the Pritzker School of Molecular Engineering at the University of Chicago. “These attributes, along with coherence time, make our electron qubit exceptionally compelling.”
“The long lifetime of our electron qubit allows us to control and read out the single qubit states with very high fidelity,”
Xinhao Li, a postdoctoral appointee at Argonne and the co-first author of the paper.
“Rather than 10 to 100 operations over the coherence times of conventional electron charge qubits, our qubits can perform 10,000 with very high precision and speed,”
Dafei Jin, professor at the University of Notre Dame
Summary
A team led by the U.S. Department of Energy’s Argonne National Laboratory has significantly improved the coherence time of a novel type of quantum bit (qubit), enabling it to perform many thousands of operations. The team’s qubits, which are encoded in the electron’s charge states and protected by a neon platform, have shown potential for scalability and further optimisation, marking a significant stride towards the development of quantum computing.
- A team led by the U.S. Department of Energy’s (DOE) Argonne National Laboratory, including Professor Dafei Jin from the University of Notre Dame, has made significant progress in quantum computing.
- They have extended the coherence time of their novel type of quantum bit, or qubit, to 0.1 milliseconds, nearly a thousand times better than the previous record.
- These qubits, known as charge qubits, encode quantum information in the electron’s motional states.
- The team’s qubit is a single electron trapped on an ultraclean solid-neon surface in a vacuum, which helps to protect the qubit from environmental disturbances.
- The team has also shown that two-electron qubits can couple to the same superconducting circuit, marking a significant step towards two-qubit entanglement, a crucial aspect of quantum computing.
- The research was funded by the DOE Office of Basic Energy Sciences, Argonne, Q-NEXT, the Julian Schwinger Foundation for Physics Research, and the National Science Foundation.
- The research was published in Nature Physics and involved collaboration with several institutions, including Lawrence Berkeley National Laboratory, Massachusetts Institute of Technology, Northeastern University, Stanford University, the University of Chicago, and the University of Notre Dame.