This site uses cookies. By continuing to use this site you agree to our use of cookies. To find out more, see our Privacy and Cookies policy.
Skip to the content

Share this

Free weekly newswire

Sign up to receive all our latest news direct to your inbox.

Physics on film

100 Second Science Your scientific questions answered simply by specialists in less than 100 seconds.

Watch now

Bright Recruits

At all stages of your career – whether you're an undergraduate, graduate, researcher or industry professional – can help find the job for you.

Find your perfect job

Physics connect

Are you looking for a supplier? Physics Connect lists thousands of scientific companies, businesses, non-profit organizations, institutions and experts worldwide.

Start your search today


When will quantum communications blast off?

Will quantum communications be sent to the ISS?

Will quantum communications be sent to the ISS? (Courtesy: NASA)

By Hamish Johnston

I think it’s safe to say that quantum communications between satellites and ground-based stations should be possible. Optical signals have already been sent 144 km through the air between ground stations at sea level. More recently, quantum communications have been achieved between an aircraft in flight and a ground station 20 km distant.

While quantum communications have been sent comparable distances via optical fibre, it’s unlikely that the fragile single photons used in such missives would survive an ocean crossing unscathed. Therefore if technologies such as quantum key distribution cryptography are to become truly practical, satellites must be involved.

The next logical step is therefore to send quantum-communications kit into space – and the cheapest way of doing this is to tag along on the International Space Station (ISS), which orbits at about 400 km above the surface of the Earth. While this is much further than 144 km, for most of this distance the atmosphere is very thin and therefore much less likely to interfere with quantum communications than air at sea level.

Leading researchers have already made several proposals to get experiments on board the ISS, but these have been turned down. Now Rupert Ursin and colleagues at the Austrian Academy of Sciences and the European Space Agency (ESA) have put together a new proposal with a twist. Unlike previous plans that involved sending quantum signals from space to ground, the team want to fire them up into space.

An important benefit of this approach, they argue, is that only a small amount of equipment must be sent up to the ISS – single-photon detectors that have already been qualified for use in space. This is unlike a quantum transmitter, which would require the qualification and launch of lasers, crystals and other equipment.

How it would work (click to enlarge image)

How it would work.
(Click to enlarge image)

Previous proposals have focused on space-to-ground transmissions because of something called the shower-curtain effect, which ESA says “can indeed be observed by looking through a transparent shower curtain while taking a shower. The view from the inside out (from behind the shower curtain) is very much blurred, while the view from the outside in (from some metres away from the shower curtain) is comparatively clear”.

The upshot of this is that a downward signal encounters much less disruption than an identical upward signal – and this is very important because the single photons that carry quantum information cannot survive much jostling en route.

But now Ursin and colleagues argue that the latest entangled photon sources are so good that a ground-to-space system could tolerate the much higher losses that result from the shower-curtain effect. Indeed, physicists would have to demonstrate the feasibility of an uplink anyway, so why not cut to the chase?

Their proposal has just been published in the New Journal of Physics and you can read the paper here.

Will it be approved? Maybe or maybe not, but I’m certain that eventually we will see quantum communication with satellites.

This entry was posted in General and tagged , . Bookmark the permalink.
View all posts by this author  | View this author's profile

One comment to When will quantum communications blast off?

  1. M. Asghar

    From what we know at present about the quatum communications on the Earth: distance covered, the amount of decoherence suffered, a good quality-and-intensity-source of entangled photons should do the job from Earth to the ISS with a good probability. All the best to the proposing team.


  • Comments should be relevant to the article and not be used to promote your own work, products or services.
  • Please keep your comments brief (we recommend a maximum of 250 words).
  • We reserve the right to remove excessively long, inappropriate or offensive entries.

Show/hide formatting guidelines

Tag Description Example Output
<a> Hyperlink <a href="">google</a> google
<abbr> Abbreviation <abbr title="World Health Organisation" >WHO</abbr> WHO
<acronym> Acronym <acronym title="as soon as possible">ASAP</acronym> ASAP
<b> Bold <b>Some text</b> Some text
<blockquote> Quoted from another source <blockquote cite="">IOP</blockquote>
<cite> Cite <cite>Diagram 1</cite> Diagram 1
<del> Deleted text From this line<del datetime="2012-12-17"> this text was deleted</del> From this line this text was deleted
<em> Emphasized text In this line<em> this text was emphasised</em> In this line this text was emphasised
<i> Italic <i>Some text</i> Some text
<q> Quotation WWF goal is to build a future <q cite="">
where people live in harmony with nature and animals</q>
WWF goal is to build a future
where people live in harmony with nature and animals
<strike> Strike text <strike>Some text</strike> Some text
<strong> Stronger emphasis of text <strong>Some text</strong> Some text