#compuation

Bright lasers

There is an article on nature.com about "Coherent storage and manipulation of broadband photons via dynamically controlled Autler-Townes splitting" and I am sure that to most of us that is just science fiction or "words that grow-ups use so we, the kids, do not understand their booty calls" :)

Photonic quantum information technologies rely on quantum memory for long-lived storage and coherent manipulation of short pulses of non-classical light. The optical quantum memories explored over the past two decades are based on various coherent light-matter interaction schemes, but despite impressive progress, practical memories featuring efficient, broadband and long-lived operation remain elusive, due to the technical demands and inherent limitations of the established schemes. Here, we introduce a technique for high-speed quantum memory and manipulation that overcomes these obstacles. This scheme relies on dynamically controlled absorption of light via the ‘Autler–Townes effect’, which mediates reversible transfer between photonic coherence and the collective ground-state coherence of the storage medium. We experimentally demonstrate proof-of-concept storage and signal processing capabilities of our protocol in a laser-cooled gas of rubidium atoms, including storage of nanoseconds-long single-photon-level laser pulses for up to a microsecond. This approach opens up new avenues in quantum optics, with immediate applications on atomic and solid-state platforms.

As I said. This is the "easy" part of the article and it has about 60 references :)

You will say, ok but what does it mean? Well, it means something on the line of "Really bright lasers that open up the atoms/atomic gas? which will then be used to store qubits"

So, using a bright laser. As someone else put it. Use a bigger hammer to fit stuff :)

In the quantum world and quantum computers, the quantum information (qubits) are transported using light (one photon = one qubit). The problem is STORING said qubit (photon) which, as you might know, are moving very very fast. So far they tried storing said photon in a very very cold gas which would do the trick but then you will need the photon (qubit) later you will have to take it out from there. So, we have slowly and carefully stored a qubit vs hammer it there with a laser.

One atom in the gas can have three states: - ground state, basically the natural state where the atom chills with his friends having a good beer (Carlsberg maybe?) - storage state basically is where the atom ends up after having the "drink" (absorbed the qubit) - transfer state, In this state the atom receives high energy necessary for qubit via a laser which stores the qubit and then changes the state from transfer to storage state. If the laser continues to shine on a stored atom it will change the state again from Storage to Transfer and the qubit is emitted as a photon again. Thus, the write/read is achieved.

By contrast, if you turn the laser off the qubit get stuck in storage state until you turn the laser back on. This works really well but it has some problems. Qubit has to have the same wavelength and the pulse of light has to be very long. Making the memory slow and, oh well, delicate.

The hammer way

Same states but this time very bright laser. If you change the power output of the laser the atom itself changes. It gives a good shake to the atom making contract and stretches making the transfer state split into two different states with a slightly different energy. This might mean that the photon will NOT be ideal for this BUT we only need the photon to overlap a bit with the wavelengths. If that is achieved then the Storage qubit state is reached. Researchers managed to prove exactly that. The researchers also have shown that their storage system is flexible because of the ability to change qubit properties. Imagine that in order to store an upcoming photon we just turn the power up on the laser and we zap it enough to absorb the photo. How about if we need the photon to come out with a specific energy? Make use of the laser control at low power to emit the qubit.

This method has the advantage of being faster than the current procedures. The control pulse is short and powerful and it stores qubits in the form of short pulses. It has the added value that we do not need to know the wavelength of the upcoming qubit. If it is the expected range we can interact with it. It can also use its adaptiveness in the case of two quantum systems. One requiring specific qubit wavelength while the other has a short duration. This read/write can convert.

Quantum computers and quantum systems are mindblowing if you think about them. Microwave systems for computation, photonic systems for transport and atomic states for memory. What an interesting and sometimes (I guess) frustrating field to be in.