As an operation unit of quantum computing , Qubits can represent 0 and 1 The superposition of two states . future , Quantum computers can solve specific complex problems that cannot be solved by any classical supercomputer .
this , The research team led by Argonne National Laboratory , And FAMU-FSU College of Engineering （ The Joint Engineering School of Florida a & M University and Florida State University ） Associate professor of mechanical engineering Wei Guo The team cooperation , Built a new quantum bit platform , Showing the potential of developing quantum computers . Relevant results have been published in 《 natural 》(Nature).
The picture is from 《 natural 》(Nature) Participants in the previous study also included participants from the University of Chicago 、 Washington University in St. Louis 、 Lawrence Berkeley National Laboratory (LBNL) And scientists at MIT .
“ Through this research , We think an important breakthrough has been made , Will make great progress in the manufacture of quantum bits , Help realize the potential of this technology .” Co author of the paper Wei Guo Say .
By freezing neon into a solid at extremely low temperatures , Spray the electrons from the heated filament of the bulb onto the solid , And capture a single electron , To make new quantum bits . When neon cools to about minus zero 248.6 Centigrade , Pressure exceeds 0.42 At atmospheric pressure , Will freeze to a solid .
Experimental related devices , The picture comes from the paper, although there are many types of qubits , The team chose the simplest one , That is, a single electron . Heat a simple filament in a light bulb you see everyday , You can easily emit infinite electrons .
One of the important properties of qubits is that they can hold for a long time 0 or 1 The state of , And is referred to as “ Relevant time ”. But the coherence time is limited , This limitation is determined by the way qubits interact with the environment . The defects in the quantum bit system will greatly reduce the coherence time .
For the above reasons , The team chose to trap electrons on the surface of ultrapure solid neon in vacuum . Neon is one of the only six inert elements at present , This means that it will not react with other elements .
In the past, liquid helium was used as the medium to preserve electrons . Although liquid helium is easy to make , But solid neon is an almost flawless 、 A material that does not vibrate like liquid helium . Vibration easily disturbs the electronic state , This affects the performance of qubits .
“ Because of this inertia , Solid neon can be used as the purest solid in vacuum , To carry and protect any qubit from interference .” Scientists at Argonne National Laboratory , Project lead researcher Dafei Jin Express .
By using a chip level superconducting resonator , Electrodes in microchips can hold electrons trapped in solid neon in place for more than two months . The team used the microwave emitted by superconducting microwave resonators , Manipulate the captured electrons , Enable it to read and store information from qubits , So it can be applied to the future quantum computer .
Superconducting microwave resonator ( golden ) Microwave can be used ( Light blue beam ) Help control an isolated electron ( Orange wave function ), The electron is trapped in a solid neon ( green ) On , The picture is from Argonne National Laboratory after the establishment of the aforementioned qubit platform , The team used microwave photons to perform quantum bit real-time operations on the captured electrons , And its quantum properties are described . Experimental tests show that , Solid neon provides a stable environment for electrons , It has very low electronic noise interference . meanwhile , The coherence time of the qubit in the quantum state , More competitive than other qubits .
“ Based on this platform , For the first time, we have realized the strong coupling between a single electron in a near vacuum environment and a single microwave photon in a vibrator ,” Postdoctoral Fellow of Argonne National Laboratory 、 First author of the paper Xianjing Zhou Express ,“ This is to use microwave photons to control each electronic qubit , And connecting multiple qubits in a quantum processor opens up the possibility .”
Scientists believe that , Practical qubits need to have three key qualities ： One , Can show consistency for a long time , That is, keep the superposition state for a long time , Ideally, more than a second ; Two , Can quickly transition from one state to another , To help you perform operations quickly , Ideally, about a billionth of a second ; 3、 ... and , Through a quantum mechanical phenomenon called entanglement , Can be scaled up , Connected to many other qubits , To achieve parallel work .
The previous experiments show that , After optimization , New qubits can keep 220 Nanosecond superposition state , Changing the State takes only a few nanoseconds （1 Nanoseconds are billionths of a second ）, The performance is better than that of previous studies 20 Charge based qubit .
The researchers believe that , By developing quantum bits based on electron spin rather than charge , It is more likely to develop coherent time more than 1 Second qubits . meanwhile , The device is relatively simple , Easier to manufacture at low cost .
at present , Researchers don't know how scalable the new system is .“ This is still a problem common to all qubit platforms ,”Dafei Jin say ,“ It is not easy to realize hundreds of qubits in the short term .”
future , The team also plans to entangle two qubits based on electron spin and charge , To achieve the goal of manufacturing dozens of qubits on the same chip .