Quantum computing

Make quantum computers using ultra-cold atoms as quantum bits of information.

Computer chip

Use lasers to make quantum computers

You can use cold-atom systems as quantum computers. Cooling lasers freeze the atoms and hold them still, mid-air, using the Doppler cooling technique. The cooled atoms will work as qubits.

Pick the right laser for quantum computing

When choosing a laser for atom trapping and cooling, there are several things to consider:

  • Power scalability
  • Narrow linewidth
  • Wavelength coverage
  • Wavelength stability
  • Fiber advantages
  • Scalable and industrial manufacturing

Power scalability

Power consumption of cold atom/ion experiments scale with the number of qubits. Diode lasers have a breaking point at 2-4 W before compromising linewidth or system temperature, while our fiber lasers can supply ~40 W of narrow power.

Narrow linewidth

Linewidth is closely tied to laser technology. The laser’s linewidth must be significantly smaller than the natural linewidth of the atom. If not, the laser will be limiting the lowest temperature reachable rather than the atom itself.  Similarly, intensity fluctuations – typically expressed as relative intensity noise (RIN) – also heats the atom and limits its cooling rate.

Our fiber lasers have linewidths in the 1-100Hz range, while SSL and diode lasers typically have a linewidth of >100Hz.

Wavelength coverage

Specific and hard-to-reach wavelengths are key to the quantum computing market. We provide lasers covering most of the visible spectrum, including harmonics of Barium transition wavelengths.

Wavelength stability

When picking a laser for atom cooling, it is important to ensure accurate wavelength control. To fine-tune the system, the absolute wavelength must be well-defined and adjustable – and it must not fluctuate.

Fiber advantages

Fiber coupling is necessary for rack mounting. Fiber lasers are inherently more stable than other laser types. Moreover, NKT Photonics’ photonic crystal fiber platform is uniquely suited to transport high-power narrow-linewidth light.

Unique fiber delivery system 

Do you want to mount the laser system in a rack? No problem. With our unique fiber delivery system, aeroGUIDE POWER, you can get light wherever you want. The fiber delivery solution handles high power, preserves the low-noise laser properties, and delivers single-mode light at all wavelengths.  

Scalable and industrial manufacturing

The fiber laser platform is highly scalable and we have experience in scaling and delivering thousands of lasers every year. Our fiber laser architecture builds on 20 years of experience with over 15,000 single-frequency fiber lasers in the field, many in harsh environments running 24/7. MTBF for the lasers is >30 years.

A laser that checks all these boxes – and more – is our Koheras HARMONIK. We have developed it specifically for trapping and cooling of atoms for quantum optic applications.

Read more about atomic trapping and cooling.

Our quantum engagements

We are part of the European Quantum Flagship, the European Quantum Industry Consortium, the Quantum Economic Development Consortium, and the Danish Quantum Community.

How do you make cold atoms?

When you want to cool and trap atoms with lasers, you need to know that – at the atomic scale – temperature makes atoms wiggle around. Reducing their movement is the same as reducing their temperature. You can cool atoms by carefully matching your atom with a laser that can emit light with the properties needed to cool that specific atom.

To cool an atom, you make it absorb energy only when it randomly moves towards the laser. After a short while, the atom begins to reemit the absorbed light but in random directions. On average, this makes the atom slow down in the direction towards the laser because it loses net kinetic energy in that direction.

Now you add a beam in all three dimensions, and the atom will be forced to slow down in all directions. This technique lets you cool the atom down to well below 1°K, depending on the atom used.

The goal is to make the atom absorb light only when it is moving in a specific direction. Atoms can only absorb light if the light is oscillating at one of the discrete frequencies allowed by the atom. For Rubidium, one of these frequencies corresponds to light with a wavelength of 780 nm. If the wavelength is longer, the Rubidium atom will not absorb it.

In a laser Doppler cooling system, the wavelength of the laser must be slightly longer than required for absorption. Now, when the atom moves towards the laser, the Doppler effect will cause the atom to experience the laser as emitting light at a shorter wavelength due to the Doppler effect. The atom will absorb a photon.

When moving away from the laser source, the atom experiences the wavelength as longer and nothing happens. You can use a magneto-optical trap (MOT) to shoot light at the atom from both directions and in all three dimensions. This cools Rubidium atoms down to a few µK and they are ready to be put to work.

In some systems, the atoms are transferred to other types of laser cooling systems to further lower the temperature before they are used.