Illuminating the future: ion well quantum computer

In recent years, quantum computing has developed by leaps and bounds, and has become the forefront of a new round of technological revolution and industrial transformation. Whether it is academia, industry or government, many countries in the world have recognized the importance of quantum computing to the new round of scientific and technological revolution and industrial development, and have invested a lot of resources to promote the development of this field. At present, there are many mainstream approaches to realize quantum computing in the world, including superconducting quantum computing, semiconductor quantum computing, ion well quantum computing, atomic quantum computing, nuclear spin quantum computing and topological quantum computing. < / P > < p > among these implementation paths, ion well quantum computing has become a powerful candidate for realizing high reliability quantum information processor and high precision optical ion clock due to its long coherence time and high calculation accuracy. < / P > < p > as shown in Figure 1, the experimental platform in the ion well quantum laboratory is often filled with various mirrors and lenses, which are used to focus the laser and trap the ions to a certain position. Although using lasers to control the ion trap, scientists have learned how to use the ion trap to make the quantum bits, the basic data unit of a quantum computer. However, this kind of laser device based on the traditional geometric optical path is now hindering the development of this field, because the method based on the traditional geometric optical path is difficult to realize the trapping and control of multiple ions at the same time. At the same time, these experimental devices are bulky, easily disturbed, and difficult to integrate, so as to go out of the laboratory and move towards practical and engineering. Recently, researchers from Lincoln Laboratory of Massachusetts Institute of Technology (MIT) have realized the quantum optical integration of ion trap for the first time by using integrated waveguide, grating coupler and surface electrode. < / P > < p > in this paper, the researchers present a fiber optic module that can be integrated into an ion trap chip to couple light into an optical waveguide etched on the chip. Through these waveguides, light of different wavelengths can be guided to the position of ion trap on the chip, so as to realize quantum computing. Most importantly, this method realizes the integration and scalability of ion well quantum chip, and paves the way for further large-scale industrial application of ion well quantum computing. 2. Fiber optics can directly couple light to ion trap chips. The whole chip is placed in a low-temperature vacuum cavity, and the waveguide structure on the chip guides light to the position of trapped ions above the chip for quantum calculation < / P > < p > calculation based on ion trap requires precise and independent control of each ion. When controlling several ions in a short distance one-dimensional chain, the free space geometric optical path can do well; but if we want to change the state of only one ion in a large two-dimensional array without affecting other ions, the traditional geometric optical path is very difficult to realize. Considering that the actual quantum computer often needs thousands of qubits, this traditional geometric optical path control method is difficult to achieve. The bottleneck of < / P > < p > prompted researchers to look for other possible methods. In 2016, researchers at Lincoln Labs and MIT demonstrated a new type of integrated optical chip. They focus a red laser beam on an optical integrated chip. The waveguide on the chip guides the light into a grating coupler, which acts as an optical damping band to stop the light and guide the light to the position of the ions. Red light is the key to perform the basic operation of quantum gate in quantum computing. The team demonstrated the operation of quantum gate based on red light in the demonstration. < / P > < p > but to perform all quantum calculations, six different colors of lasers are required: preparing the ion, cooling it, reading each energy state of it, and executing a quantum gate. With such a new chip, the team has extended their proof of concept to the remaining wavelengths from UV to IR. This animation shows that the grating coupler in the chip can control and measure the ion trap by emitting four wavelengths of laser. The yellow surface in the animation is the metal electrode layer on top of the chip. “Based on these wavelengths, we can perform all the basic operations of the ion trap,” says John Chiaverini, another author of the paper. One operation they failed to demonstrate – the double qubit gate – was verified by a team from eth. Eth’s team uses chips similar to those they worked on in 2016, which is also reported in this issue of nature. Chiaverini added, “their work combined with our work demonstrates that this method can be used to fabricate large-scale ion trap arrays.” < / P > < p > in order to be able to upgrade from one wavelength to multiple wavelengths, the team designed a method to prepare optical fiber modules directly on a chip. The module consists of four optical fibers, each corresponding to a specific wavelength range. These fibers are coupled with different waveguide structures etched on the chip. Robert niffeenger, the first author of the paper and the main author of the experimental part of the paper, said, “coupling the fiber module to the waveguide structure on the chip and coating the epoxy resin at the same time feels like we are in surgery. This is a very precise work. The acceptable error range of our ion well quantum chip processing is only 0.5 μ m, and it is necessary to ensure that the chip can work normally at a low temperature of 4K < / P > < p > the researchers covered the surface of the waveguide with a layer of glass, and the glass was covered with metal electrodes, which kept the ions in the right position. The metal electrode is covered with holes to radiate light in the correct position of the grating coupler. < / P > < p > because the smaller the wavelength is, the greater the loss is. Therefore, it is a great challenge to transfer light to ions with low loss while avoiding the absorption or scattering of the medium. “It’s a process of developing materials, drawing waveguide patterns, testing samples, measuring performance, and then trying again,” said sage, who was involved in the experiment. We must also ensure that the waveguide material not only works in accordance with the required wavelength of light, but also does not interfere with the metal electrodes that capture ions “In the future, we can combine these chips into arrays to integrate more ion wells, so that each ion trap can be precisely controlled, thus opening the door to more powerful quantum computers.” Daniel Slichter, a physicist from the National Institute of standards and technology, commented on this important breakthrough: “this scalable technology will enable complex systems with many lasers to operate in parallel, and have strong anti-interference ability for vibration and environmental conditions, which is essential for the realization of quantum processors with thousands of ion wells. ”The advantage of this kind of optical integrated chip is its strong anti-interference ability. For the laser on the experimental platform, any vibration may make the operation of ion trap wrong. When the laser beam is coupled with the chip, the vibration effect can be effectively eliminated. This kind of anti-interference ability is very important to improve the “coherence” of ion trap, or to extend the calculation time of qubit, and it can also greatly improve the portability of ion trap sensor. For example, atomic clocks based on ion traps can time more accurately than current standards, and can improve the accuracy of global positioning systems that rely on the synchronization of atomic clocks on satellites. The fiber optics integrated into the chip can provide all the laser beams needed to control the ion trap, which can be used in quantum computing and sensing. Sage, one of the authors of the paper, said, “we see this work as a successful example of connecting science and engineering, because this breakthrough has a great impact on both academia and industry. We need to make quantum technology robust and portable, and make it easy for people with non quantum physics backgrounds to use it. At the same time, the team hopes that this platform can help promote academic research. Chiaverini, another author of the paper, said, “we hope that more research institutions will use this platform so that they can focus on other challenges – for example, programming and running quantum algorithms based on ion wells on this platform, thus further opening the door to the exploration of quantum physics.”. Continue Reading865 optimization is different? These mobile phones should teach you a lesson!