The researchers "wrote" the quantum state of individual photons inside a rubidium atom and read the state again after a certain storage time
Scientists from Germany managed to store quantum information inside a single atom. The researchers "wrote" the quantum state of individual photons inside a rubidium atom and read the state again after a certain storage time. This method could, in principle, be used in the development of powerful quantum computers and in the establishment of their network that can transmit information and data over a considerable distance.
Quantum computers will one day be able to handle computing tasks that today take several years, using existing computers. These computers will get their great computing power from the ability to simultaneously process a variety of information stored in the quantum state of microscopic physical systems, such as atoms or single photons. In order to operate, these quantum computers will need to transfer these bits of information between their separate components. Photons are particularly suitable for this purpose, since it is not necessary to transfer any matter through them. Material particles will be used, on the other hand, to store and process information. In light of this, researchers will look for methods by which it will be possible to transfer quantum information between photons and matter. Although this has already been done using collections of thousands of atoms, physicists from the Max Planck Institute in Germany have now demonstrated that quantum information can be transferred between individual atoms and photons in a controlled manner.
Using a single atom as a storage unit has several advantages - the most important of which is the most extreme miniaturization possible - a single atom. The stored information can be processed by making direct changes to the atom, a particularly important feature for the execution of logical operations in quantum computers. "In addition, our method makes it possible to check whether the quantum information stored in the photon has indeed been successfully "written" in the atom without destroying the quantum state," explains one of the researchers. Therefore, it is possible to verify at any early stage whether the information processing stage must be repeated due to a storage error, or not.
The fact that until recently no one was able to transfer quantum information between photons and individual atoms lies in the fact that the interaction between light particles and atoms is very weak and they hardly "feel" each other. The German researchers managed to overcome this obstacle through a sophisticated tactic. They placed a rubidium atom between the mirrors of an optical resonator and then used very weak laser pulses to inject individual photons into the interior of the resonator. The mirrors of the resonator bounced the photons back and forth several times, an action that significantly increased the interaction between the photons and the atom.
The photons contained the quantum information in their polarization mode. This polarization can be left-handed (the direction of rotation of an electric field is counterclockwise) or right-handed (clockwise). The quantum state of the photon can contain both polarization states at the same time, a state known as "superposition state".
The physicists measured the storage time, that is, the time that the quantum information can be preserved in the rubidium and found it to be about 180 microseconds. "This value is similar to the storage times of previous quantum memory devices that were based on collections of atoms," notes the researcher. At the same time, a significantly longer storage time is needed in order for the method to be used in a quantum computer or quantum network.
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man,
There is no detail about the procedure used for reading or writing in the short article that appears, therefore I will write you my opinion that it should be taken with a limited guarantee due to the lack of information in the article.
There is a fundamental difference between checking that "the quantum information stored in the photon was indeed "written" successfully" and knowing what the quantum state is (it is more correct to say measurement of the quantum state). According to my understanding, the quantum information in the photon (polarization direction) is transferred to the atom (more on that later), in this process the photon is swallowed by the atom. Therefore it is enough to check whether the photon is still in the experimental system to know whether the information was written inside the atom. A measurement of the type of whether the atom is in the system or not is not a measurement of the state of polarization and therefore does not cause the collapse of the quantum information.
Regarding the way of writing in Atom. The process of absorbing a photon in an atom preserves the total angular momentum and the charge in the z direction, which are the "quantum numbers" that characterize the process. A photon has angular momentum 1 regardless of its polarization direction but the direction of its inscription dictates the charge of the angular momentum in the z direction. Therefore the type of electronic transition allowed in the atom following the absorption of a photon depends on the polarization of the momentum of the photon and the final atomic state will therefore depend on the direction of polarization of the absorbed photon.
Ehud, thank you for the reply,
The quote that surprised me in the article is:
"In addition, our method makes it possible to check whether the quantum information stored in the photon is indeed "written" successfully in the atom without destroying the quantum state,"
From what I've read and heard so far (as you wrote in your response), reading the quantum state causes the collapse of the wave function. And what I understand from this is that the reading/measurement affected the information we read.
My focus is reading and writing/preparing a quantum state for a single particle. If the operation of preparing the situation
The quantum is the same operation that is used to measure the quantum state (as I gave an example with Alec in the previous response), since a quantum state can be written by a read operation as you wrote.
And hence it is clear why the measurement causes the collapse/convergence of the state.
My question is a more technical question, how is the quantum state of the photons written? (the example given in the article)
And is the measurement of the situation done by the same mechanism?
According to this article, they managed to separate these 2 operations (writing/reading) at least in relation to the quantum state of the atom.
Gil Shalom,
Lithium and sodium are also used. Dr. Lev Haikovitz has a laboratory in Bar-Ilan that cools lithium atoms and one of the Nobel Prizes for creating the Bose Einstein condensation was received by a group from MIT that used sodium. It seems to me, but I'm not an expert, because it's easier to work with rubidium, partly because lithium is toxic and for other technical reasons.
I'm sorry but I don't have a link to a place where you can clearly read about laser cooling. Try reading about Bose Einstein BEC condensation and there you will surely find links to cooling methods. I will be happy to try to answer your questions even though I am far from being an expert in the field. In principle, the cooler is divided into 3 stages, each stage can only cool up to a certain level. The first stage is a Doppler cooler built on deceleration through photon scattering. The second stage is cooled by lowering the potential barrier of the trap in which the gas is trapped. This stage is similar to cooling a cup of coffee by blowing on it. The speed distribution of the atoms changes when the fast atoms escape from the trap. The last stage for which the Jewish physicist Cohen Tannogi received a Nobel Prize is called Sisyphean cooling and is a bonus in which the actual cooling was better than the theoretical estimates. In general, it is possible to cool to microKelvin easily and to temperatures of tens of nanoKelvin using laser cooling.
Ehud Shalom,
Thanks for the answer, but I didn't understand why specifically rubidium and not, for example, sodium or lithium with a single free electron in the shell? If you could give a link to read about cooling using a laser I would appreciate it.
man,
Reading the quantum state of the computer is a measurement, it causes the wave function to collapse into one of the base states that span the solution space. The idea in the quantum algorithms is to perform the calculation in such a way that it increases the amplitude of the solution over all the other states so that in the measurement the wave function will collapse into the solution of the problem that one wishes to calculate.
I'm not sure what you mean by determination, but before you start a quantum computer, you need to initialize it, that is, determine the initial wave function of the computer. . For example, the basic state of a system of spins in the presence of a strong magnetic field (and this is not a measurement) is a state in which all the spins are oriented in the direction of the field. After the initialization, the demagnetization can be removed in the hope that the operation will be carried out so that it does not change the state of the spins.
When you talk about the transfer of an electron in a magnetic field you are already talking about a specific implementation of a quantum computer. An implementation based on spins and determining their state using magnetic fields. You are also talking about photons and since I am not clear about the physical configuration and how it is used for quantum computing, I have difficulty answering your question. If you elaborate more, I may be able to help you, but for that I need more details.
to love
Could you expand a bit on the reading of a quantum state.
Popular science articles and books state that reading a quantum state actually fixes it
(collapse of the wave function).
I happened to see on the Internet a lecture by Leonard Susskind in which he described determining and reading the spin of an electron.
The mechanism for both actions is the same (the transfer of the electron in a magnetic field), when in the reading it is checked whether a photon was released.
In such a situation it is clear (relatively) why the reading of the quantum state determines it.
- Is reading/determining the quantum state of photons also used in one way?
- And if so, what are the thoughts/experiments for finding separate quantum reading/determining mechanisms?
sympathetic:
I really don't know, but I'm less pessimistic.
Even what is described in the current article - which is relevant to quantum computing - they have not been able to do so far and now they have succeeded.
Therefore, the research must continue and it is certain that its results will be important: either it will be proven to contradict the existing physical theories (which is an important achievement in itself) or the quantum computer will be built (which is certainly an important achievement).
It seems to me that your words, whether on purpose or not - if they have too much influence - can at most achieve a halt to the research and prevent reaching these two results.
Not everyone who goes against the establishment is right.
R.H.
Unfortunately I don't have the free time to write an article for Iden and I regret it. I try my best to try to enrich the articles with my knowledge in various fields so that readers can understand a little more deeply what is described in the articles.
Regarding your question why I believe that it is not possible to build a quantum computer. First the scientific reasoning:
A quantum computer utilizes the principle of superposition to store and perform operations on states in parallel.
In order for a quantum computer to function, it must be disconnected from its environment. In general, it is forbidden for the information about the state of the computer to leak into the environment because this is equivalent to measurement and thus will cause the collapse of the wave function. On the other hand, to carry out the logic gates in a quantum way (the calculation operations) an intervention from the outside is required, that is, a strong coupling to the environment. So we have a double-edged sword, on the one hand, a weak coupling to the environment is required, on the other hand, a strong coupling. There are attempts to perform a quantum calculation in such a way that the information in the computer is stored topologically (topological quantum computing) and is therefore immune from the environment, but I am not aware of any experimental success in this field. In addition, several ideas were put forward about performing the computing in decoherence free sub-spaces, but they were also only partially successful.
The practical reasoning: the field of quantum computing has existed for more than 15 years, since Shore devised his algorithm, experimenters all over the world have been trying to build a quantum computer without success. It is not a lack of budgets as there is a tremendous economic future for the field and therefore it receives very substantial funding. It is true that there is no guarantee that if a project is not successful it is doomed to failure, but in my opinion the progress achieved over the years is too slow and there are fundamental reasons for this.
In addition, there is the problem of scale-up, transferring a laboratory system to a system several orders of magnitude larger. This is more of an engineering problem than a principle, but sometimes it burys projects.
You mentioned Amir Yacovi's lecture, I didn't know he was involved in the field and I was interested to hear what he said. By the way, many lecturers usually mention the connection to quantum computing in their lectures because it is an elegant way to get funding.
Michael,
The works I wrote in the field of quantum computing, were how to build a quantum computer, some of them received quite a bit of resonance and one of them even received more than 100 citations. Despite the relative success, I still believe that it will not be possible to build a quantum computer. Regarding the possibility of writing a paper explaining why it is not possible to build a quantum computer, there are several reasons why such a paper cannot be published.
First, to prove with certainty that something cannot be done, it must be shown that it is against a law of nature, and this is not the case with a quantum computer. There are fundamental problems in our understanding of quantum theory at its core and which questions relate to the construction of a quantum computer, that is why the research in this field is so fascinating, but in recent years there has been no progress in understanding the foundations of the theory. Therefore, as long as it is not clear that building a quantum computer does not contradict a natural law, it cannot be mathematically proven that it is impossible. On the other hand, for two decades attempts were made to build such a computer with tremendous funding and failed. Isn't there an indication that something is missing? As long as it is not possible to substantiate mathematical claims, these are feelings of those involved in the field, as I have already written to you, and they do not write articles or receive grants on feelings. My feeling is based on the physics of the computer and you are welcome to read my answer to R.H. Going forward. In addition to this, there are dozens of examples of systems that worked well in the laboratory, but an attempt to produce their commercial prototypes failed miserably, this is a well-known scale-up problem.
A little about the politics of science. When there is funding for a certain field of science and it has a financial guarantee, articles showing that the research in this field is futile will not be published easily. See, for example, the opposition that Nir Shabiv encounters and he only claims that only one third of global warming is man-made. His articles are not published easily and he does not receive many grants. This is the way of the world. So there is not much promise in writing articles about the impossibility of building something as you advised me.
Dudik:
you are welcome! Build!
The time has come for a quantum computer!!!
How much longer can we wait?!?
And people, there is no reason why a quantum computer won't be built, it's all a technological matter,
Controlling the atomic level is already achievable, in terms of potential investment, this is a tremendous field that will strengthen humanity's computing capabilities, perhaps like the introduction of the computer in the 80s-90s
sympathetic,
Can you explain to laymen why you think a quantum computer will not be built? Maybe even as an article for information?
I actually heard a lecture about a year ago by Prof. Amir Yacovi from Harvard who estimated that such a computer would indeed be built.
sympathetic:
The funding can also be obtained for work that will convincingly show that this cannot be done.
Such work has value for several reasons, among them:
1. It can save a lot of money that you think is wasted.
2. It can - from the point of view of the optimists among the investors and scientists - point to what has already been tested and rejected and thus direct them to what has not yet been rejected in a sufficiently convincing manner.
Did you do this kind of work?
If so - who was convinced and why weren't the others?
If not - maybe it's worth it? I guess you also wouldn't mind receiving a research budget and investing it in a cause that seems justified to you.
R.H.
I am not predicting, but expressing my assessment, in exactly the same way as those experts who believe that it is possible to build a quantum computer. As part of my research, I have had the opportunity to collaborate with a number of world experts in the field and even publish articles with some of them, and I believe, although I have not heard them state so in Rish Gali, that they believe that today quantum computing is faced with problems that are not solvable unless a fundamental breakthrough occurs (which is indeed difficult to predict regarding him).
Regarding Michael's reasoning based on the fact that people are still working in the field, science and politics are not disconnected as you probably know and money goes to fields with tremendous economic promise. If a quantum computer is built, it will have far-reaching consequences for the entire field of information storage in the world (as a result of Shor's algorithm, which shows that large numbers can be sorted relatively easily), and therefore it is an economic interest first and foremost. In addition, scientists study the field because it is interesting and has fundamental questions in quantum theory. So the fact that people research a certain field does not necessarily indicate their views on success but sometimes their areas of interest and their possibility of receiving funding.
sympathetic,
I agree with Michael here. I recently read a book about predictions by experts in all fields that went wrong. What I learned from the book is that, as Nils Bohr already said: prediction is a difficult matter, and predicting the future is doubly difficult."
sympathetic,
Go away, it's not your honor to deal with ghosts.
Ghosts:
I think your rant about Ehud is really exaggerated.
From his responses it is easy to learn that he knows the subject of quantum physics very well.
With all your (really) impressive progress in understanding physics over the short period of our acquaintance, it seems to me that your knowledge in the field still does not begin to approach his.
So a little country road won't hurt.
That doesn't mean I accept his predictions.
I don't know enough about quantum computers to have an opinion.
I draw, however, encouragement from the fact that many others - whose knowledge in the field probably does not fall short of Ehud's - are still dealing with the issue - something they would not have done if they did not believe it had a chance.
I suggest that we all wait for a consensus to form on the subject and do so while preserving the respect of others.
R.H. Ghost 0
Some people just don't even deserve a response.
Wow.
I've seen retarded comments before in my time on this site, but these are… a whole other level.
Refam, allow me to solemnly declare for the third time: you are an idiot!
In general, Mr. Ehud, don't get lost, but you portray yourself as a failed scientist who seeks refuge in scientific websites - that's probably why you're afraid to identify.
Where do you even find time to comment here? Don't you have a computer to build?
Lost
I didn't expect you to react like that. I am truly embarrassed by your humiliation.
You don't want to give details about yourself just for the reason that you can continue to write nonsense from time to time and not worry that at your place of work someone will read your delusional comment and understand who you really are.
In addition, when you write that you know that a Konti computer will not build - based on your personal knowledge, then it only proves that you do not know what you are talking about.
I am sure that the articles you wrote did not innovate anything either. I'm also sure that what you wrote in those articles is similar to what the average person would write about tomorrow's weather.
If you really understood something about this, you would not have the need to hide from others.
I don't want to answer you the truth. I'm really disgusted when I read your comments even if you only write about physics.
R.H. Ghost 0
When you are caught in your ignorance you start insulting. As usual you do not know what you are talking about and you do not understand the discussions you are reading.
I don't like to give unnecessary details about myself and I prefer to conduct discussions based on my own facts, but since you threw mud,
So, yes, I actually dabbled in the field of quantum computing and wrote more than 5 articles on the subject in leading scientific magazines. When I present my opinion that a quantum computer will not be built, I do not commit to it, I speak from my knowledge in the field (while knowing the main problems in the field) which gives the impression, at least to me, that it is much more grounded than yours.
Let's get back to you for a moment. Do you know what a quantum computer is or are you just rambling as usual?
Mr. Ehud
I can answer your question. But first you answer me, on what basis do you determine that a quantum computer will never be built? I assume you are a prophet because otherwise it is impossible to explain your strange reaction.
Do you even know what a quantum computer is?
Are you in this field? I do not think so .
That's why you don't know what you're talking about, the main thing is that you think you know and what's more, you allow yourself to pass a stupid "criticism".
I did, but you're supposed to be a pretty educated person, isn't it a shame that you humiliate yourself?
The fact that you have learned something about quantum theory does not mean that you understand what a quantum computer is. And it will be true that on this topic you will learn instead of jumping with envy every time someone says something you didn't know.
Besides, we've already seen how educated you are on subjects you're not familiar with!
That's why it's better not to just respond to the following unless it's only on a topic you understand.
R.H. Ghost O
You're rambling again without understanding what you're talking about... You always respond as if you have a basic understanding of topics you know nothing about and even bother to comment on other commenters.
It is clear that you do not know what quantum is in a quantum computer. Have you ever taken a course in quantum theory? Would it be helpful to explain to me what a quantum is in a quantum computer? Do you know what the requirements are for a quantum computer? I assume that since quantum theory is a physical theory that works on atoms and molecules, then everything that is made up of them, and in particular a computer, are quantum.
You claim that a quantum computer does not require long-term memory storage, so what does it mean?
If you want to continue this discussion, please write to me what are the requirements for a quantum computer (I also ask that you write them yourself and do not refer me to a website or book that you do not understand what is written in them).
By the way, Anat, this was also published in Nature:
A Single-Atom Quantum Memory
Nature, Advance Online Publication, May 1, 2011; DOI: 10.1038/nature09997
I understand that you think that Nature is not as updated as you.
Advertised as a public service as part ofThe button war
And another thing:
Long-term memory storage is not necessary to build a quantum computer.
For example, in a biological brain there is a mechanism that knows how to save information for the long term and there is a similar mechanism that saves information for the short term.
Initially, it is possible to build a quantum computer that knows how to save information for a short time in order to perform any operation or calculation and then transfer/store the data in another place that will be designated only for that purpose.
Anat:
I think you made the creator.
There is a button that you have that means that when news is published in certain fields you have to try to create the impression that you know better.
Since you always (but always!) do this only in the form of a statement without any supporting evidence, then in cases where you assert your claims in front of people (or entire institutes) that the published news is in their field of expertise - I find it appropriate to comment on this.
Yes! I confess! I have a button that is activated by unfounded contempt for other people - especially if they are those who, unlike you, have proven themselves to be serious.
So now we discovered another button in you: you don't know how to accept criticism. Criticism triggers a violent reaction in you (but fails to make you substantiate your words).
Anat
In your response to Michael Rothschild, it would have been correct if you had attached proof of your words, otherwise you will not be taken seriously.
sympathetic
In my opinion, the quantum computer will eventually be built, although the road is still very long, but nevertheless a "quantum computer" at least in my opinion is something that is inevitable.
The whole idea is to build a system as small as possible that will allow the execution of as many operations as possible and in the shortest possible time. Similar to the brain - which is built of atoms first of all, and only because of a certain arrangement of the atoms is the proper functioning of the brain possible - so is the computational system at the quantum level that we strive to reach - which will allow operations to be performed in a manner similar to a biological brain.
In other words, the quantum computer is also a type of future biological brain - if you take into account the fact that the brain is constantly developing and also changing its shape (after all, no one knows what such a computer will look like - it does not have to be made of iron or steel or rubber and such. If it is a matter of the quantum level - a system The macro can be biological). That's my opinion at least.
Michael Rothschild:
You're like a doll whose button you press and then she starts talking or I'm a prophet and I knew in advance that you would have some wisdom to say
OK, so here it is: "The researchers "wrote" the quantum state of individual photons inside a rubidium atom and read the state again after a certain storage time" several years ago.
It's possible that the original article has something really new and you didn't translate it and it's possible.
Oops, it looks like I clicked one of your buttons again by mistake.
Gil Dotan,
Rubidium is used because it belongs to the alkyl elements, it has full electronic shells and in the outer shell (which is not full) a single atom. In practice, alkyls can be considered as a type of hydrogen atom. An atom with a single electron. why is it important? When an atom has a single electron, it can be relatively easily cooled to very low temperatures. It was Eric Cornell and Carl Weinman who received the Nobel Prize in 2001 for the Einstein bouse condensation they obtained with rubidium. Also in Israel at the Weizmann Institute in the laboratory of Prof. Nir Davidson they created a Bose Einstein condensation of rubidium atoms. If you are interested, read a bit about cooling methods of atoms using lasers.
Anat,
You are right that the various components have been played with for years, but as Michael already wrote to you, this is probably the first time that they were able to write and read situations from a single atom.
Nadav,
I am not at all sure that they will ever succeed in building a quantum computer. Today they know how to perform quantum calculations, but it is not yet a computer. Many ideas in science have been proven in the micro, but it turned out to be impossible to translate them to the macro. A mathematical proof is not enough to show that something is applicable.
Aaron,
You are right because you have to keep the memory for a long time to produce a quantum computer. Although I don't understand how you got to 5 minutes, in my opinion the relevant time is seconds if not milliseconds and it is determined according to the speed at which calculation operations can be performed.
Anat:
At the beginning of the article it is written in bold letters "The researchers "wrote" the quantum state of individual photons inside a rubidium atom and read the state again after a certain storage time".
If they haven't done it before - it's a novelty - just as the flight to the moon was a novelty even though they had already played with aircraft years before.
Do you think the people of the Max Planck Institute do not know what has already been done and what has not been done?
It is not clear what is new in this article since several years playing with single rubidium atoms and single photons in resonators something from 2002
Admittedly still confused. When magnetizing a chip, only electrons move, are they considered "matter"?
W. Doc:
It does look like a translation error:
The original wording is Photons are particularly suitable for this, as no matter needs to be transported with them
The meaning is that for the purpose of transferring information in photons there is no need to transfer material (and in fact - no material is needed at all).
This was said - in opposition to the matter of storing and processing the information for which the material is needed.
The sentence "Photons are particularly suitable for this purpose, since there is no need to pass any matter through them. Material particles will be used, on the other hand, to store and process information. In light of this, researchers will look for methods by which it will be possible to transfer quantum information between photons and matter." is not clear
Through what should or should not transfer material?
Aaron, it doesn't matter if it's 180 microseconds or 10 microseconds. Even in today's DRAM memory, the memory is refreshed every cycle time (you can easily calculate it, today's memory frequency is almost 2 gigahertz).
And like everything mathematically proven in this pesky humanity, the question is only when, not whether.
I meant the world
It looks like only a laboratory experiment, I don't believe that they will ever be able to save a memory in this way for 5 minutes, a quantum computer will not be built for the future
Why exactly rubidium...?
L1: I don't think we need this effect to get this storage capacity. A grain of sand has 20,000,000,000,000,000,000 atoms, so it can store vast amounts of information through proper spatial organization. Of course, provided we know how to control the atoms at the required level.
Amazing. It is basically a realization of Feynman's storage idea.
If I remember correctly, Feynman calculated and found that all human knowledge written in books and drawn in paintings can be stored in something like a grain of sand :-).
And it is interesting if there is a theoretically known reason for 180 microseconds or if it is an unexplained measurement result. This is interesting in the context of wave collapses or decoherence.