The race to lead in quantum computing is not just a matter of two. Currently, the United States and China lead the way, but other countries, including Germany, France and the United Kingdom, are also making important contributions with a very clear purpose: to acquire a solid technological base in this discipline.
In the medium term, quantum computing, if it continues to develop as it has done over the last decade and gradually overcomes the challenges that still remain to be resolved, will make a difference not only in the field of scientific research; also in telecommunications, economy or in the very sensitive field of cryptography, among other critical areas for many nations.
The countries that I have mentioned in the first paragraph of this article, and some others, have embarked on a long-distance race to avoid being left behind, but beyond this international pulse there is a strictly technical struggle that is going relatively unnoticed outside the scientific field.
What is interesting is that in this context the leading role is not held by the countries that seek to lead in quantum computing; It is called for by the most advanced technologies that are being used to manufacture qubits. However, that in a field in which so much remains to be done that we have several options on the table is great news. Far from being a problem, any innovation that allows us to develop more and better qubits is welcome.
Superconducting qubits have one trump card in their favor: great scalability
Having quantum computers with many qubits is crucial. And it is not only because by increasing the number of qubits it is possible to carry out many more calculations simultaneously, but also because in order to make these devices capable of make up for your own mistakes it is essential to have more qubits. many more.
Osprey, the most advanced quantum processor to date, is from IBM and has no less than 433 qubits
The most advanced quantum processor developed to date, known as the Osprey, was presented by IBM in mid-November, and it has 433 qubits. This company plans to have a quantum chip of no less than 1,121 qubits ready in 2023. If this progression is confirmed, come from IBM or any other company, the first quantum processors with more than one million qubits will arrive in a few years , and just at that moment quantum computers will reach a tipping point.
During the conversation we had with Ignacio Cirac, a Spanish scientist unanimously considered one of the founding fathers of quantum computing, last June he explained to us how many qubits a quantum processor must have to be able to solve truly significant problems and implement the long-awaited bug fix:
The number of qubits will depend on the type of problems we want to solve with quantum computers. To tackle symbolic problems we will need to have several million qubits. Probably even hundreds of millions of qubits. Right now we are talking about a hundred qubits, so there is a long way to go. There are people who say that with 100,000 qubits maybe a specific problem can be solved, but really, a lot of qubits are needed.
There is no doubt that much remains to be done. Very much. But the researchers are on it. And, furthermore, they are not following a single path. There are currently two technologies that are showing enormous potential not only because of their ability to allow us to increase the number of qubits in quantum processors, but also because they are allowing researchers to fine-tune higher quality qubits.
As the quality of a qubit increases, the greater is its ability to resist quantum decoherence, which is the phenomenon that appears when the quantum effects that give these computers an insurmountable advantage over classical supercomputers vanish. This is why it is crucial not only to have processors with more qubits, but also to tune higher quality qubits.
Intel is working to increase the scalability of its quantum processors by applying in their manufacturing the knowledge that this company has accumulated during decades of producing CMOS devices.
The technology that companies such as IBM, Google or Intel, among others, are using to manufacture their quantum processors uses superconducting qubits, which are characterized by working at a temperature of about 20 millikelvins, which is approximately -273 degrees Celsius. It is imperative that they operate with as much isolation from the environment as possible and at such astonishingly low temperatures.
IBM aims to have a quantum processor with 1,121 qubits by 2023, and its competitors are likely to be hot on its heels
And it is because this minimum energy level allows them to extend the time during which the quantum states of the system are maintained, and, at the same time, also postpone the moment in which quantum decoherence appears. Quantum states are maintained for a limited period of time, and this time is precisely what we have to perform quantum logic operations with the qubits of our computer.
One of the greatest successes that superconducting qubits are achieving is precisely how fast they are allowing the number of quantum bits to scale. As we have seen, IBM aims to have a quantum processor with 1,121 qubits in 2023, and possibly Intel, Google and the quantum chips being developed by China will experience a similar development.
In fact, Intel has announced that it is working to increase scalability of its quantum processors applying in its manufacture all the knowledge that this company has accumulated during decades of production of CMOS devices. In fact, the background that both this company and IBM have in the field of semiconductor production works in their favor because all this knowledge is being very useful when it comes to tackling the progressive refinement of their superconducting qubits.
Ion traps are the main alternative to superconducting qubits
This is the path that IonQ and Honeywell are following, and it seems to be getting good results. In this article we are not going to delve into the operation of this technology so as not to complicate it too much (we can do it in another report if you are interested in this topic and you confirm it in the comments), but it is interesting that very broadly we can intuit what its strategy to identify how superconducting qubits differ from those that use ion traps.
These last use ionized atomsTherefore, they have a non-neutral global electrical charge that allows them to be isolated and confined within an electromagnetic field. This is the starting point of this technology, and from here the strategies used by IonQ and Honeywell, which are the companies that have decided to follow this path with more impetus, to manipulate these ionized atoms and carry out logical operations with them differ. slightly.
The ion-trapped qubits being used by IonQ and Honeywell are more robust than superconducting qubits, allowing them to effectively dodge quantum decoherence for longer.
IonQ acts on the quantum state of its qubits with ion traps, cooling them to reduce the computational noise level, and using lasers right after to operate on them. But it doesn’t use a single laser; it uses one for each ion, and also a global laser that acts on all of them simultaneously. Honeywell also uses ionized atoms and lasers, but the procedure it uses to establish entanglement between two ions and act on them with a laser is different from that used by IonQ.
In any case, the most interesting thing is that both Honeywell and IonQ ensure that their ion-trapped qubits they are more robust than the superconducting qubits used by its competitors. And this means, as we have seen a few lines above, that they manage to preserve the stability of a quantum state for a longer time, which allows them to carry out, always according to these companies, more operations with their qubits before quantum decoherence appears. .
Ions implanted in macromolecules and neutral atoms arrive stomping
Although, as we have seen, superconducting qubits and those using ion traps are currently the most developed, they are not the only technologies within our reach. Many research groups are working in this area, and some promising lines of research propose different ideas than the two we have just investigated.
Juan José García Ripolla researcher at the Institute of Fundamental Physics of the Higher Council for Scientific Research (CSIC) who develops his research activity within the Quantum Information and Fundamentals of Quantum Theory group, tells us about one of them:
There are experts in Spain who work on quantum computing with molecules. They implant ions in macromolecules, store the information in them and can do small calculations. It is a very unique line both in Europe and in the world that could be strengthened. There are many areas in which something differential can still be achieved and in which Spain can contribute in a singular way.
Ignacio CiracOn the other hand, he confirmed to us during the conversation that we had with him the greater robustness of ion-trapped qubits compared to superconducting qubits. And, incidentally, he told us about another very promising technology, which reminds us that, fortunately, there are several attractive lines of research open that seek to develop more robust and stable qubits:
Superconducting qubits will probably help us to have more qubits, but we think they will have more errors than ion qubits. There is also a third technology, neutral atoms, on which various research groups are working and which is managing to gather more qubits while maintaining the accuracy and lack of errors of the other systems. I hope that very soon we will be able to develop more advanced technologies that will surpass those we have today.
Images: Honeywell | IonQ | Intel
