<story><title>Chinese satellite is one giant step for the quantum internet</title><url>http://www.nature.com/news/chinese-satellite-is-one-giant-step-for-the-quantum-internet-1.20329</url></story><parent_chain><item><author>xgbi</author><text>&amp;gt; Eventually, quantum teleportation in space could even allow researchers to combine photons from satellites to make a distributed telescope with an effective aperture the size of Earth — and enormous resolution. “You could not just see planets,” says Kwiat, “but in principle read licence plates on Jupiter’s moons.”&lt;p&gt;Uh, what? What does entangled photons have to do with interferometry-based astronomy?
Can somebody explain to me how this could be achieved?</text></item></parent_chain><comment><author>Strilanc</author><text>It lets you bypass some classical limits. It&amp;#x27;s a well known idea. For example, John Preskill mentioned entangled telescopes in a non-technical talk back in February [1].&lt;p&gt;A specific case is &amp;quot;NOON&amp;quot; states [2]:&lt;p&gt;&amp;gt; &lt;i&gt;NOON states are an important concept in quantum metrology and quantum sensing for their ability to make precision phase measurements when used in an optical interferometer.&lt;/i&gt;&lt;p&gt;---&lt;p&gt;Here&amp;#x27;s an example that doesn&amp;#x27;t exactly use entanglement, but does use quantum stuff to give you the general flavor. Suppose you have an optical setup like this:&lt;p&gt;&lt;pre&gt;&lt;code&gt;          B
          |
          v
    A --&amp;gt; ◩ -----&amp;gt; D1
          |
          |
          v
          D2
&lt;/code&gt;&lt;/pre&gt;
When a photon is emitted from A, or B, it passes through a beam splitter then continues on to the two detectors and triggers one of them. If the detectors are classical, then there&amp;#x27;s no way for you to distinguish whether A or B emitted the photon. Both are a 50&amp;#x2F;50 split. But if the detectors can store their readings at various times as quantum information and keep that information coherent, then you can bring the stored qubits together, simulate un-applying the beam splitter, and voila! The same basic idea applies to telescopes: photons from different sources spread out in slightly different ways, and we can undo some of that spreading with quantum computation.&lt;p&gt;1: &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;youtu.be&amp;#x2F;lN8zT_Yk5sg?t=3m58s&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;youtu.be&amp;#x2F;lN8zT_Yk5sg?t=3m58s&lt;/a&gt;&lt;p&gt;2: &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;NOON_state&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;NOON_state&lt;/a&gt;</text></comment>
<story><title>Chinese satellite is one giant step for the quantum internet</title><url>http://www.nature.com/news/chinese-satellite-is-one-giant-step-for-the-quantum-internet-1.20329</url></story><parent_chain><item><author>xgbi</author><text>&amp;gt; Eventually, quantum teleportation in space could even allow researchers to combine photons from satellites to make a distributed telescope with an effective aperture the size of Earth — and enormous resolution. “You could not just see planets,” says Kwiat, “but in principle read licence plates on Jupiter’s moons.”&lt;p&gt;Uh, what? What does entangled photons have to do with interferometry-based astronomy?
Can somebody explain to me how this could be achieved?</text></item></parent_chain><comment><author>MalcolmPF</author><text>This also made me raise an eyebrow. I found a preprint[0] of an article on the subject after some googling. I&amp;#x27;ve only skimmed it so far but it seems promising.&lt;p&gt;[0] &lt;a href=&quot;http:&amp;#x2F;&amp;#x2F;arxiv.org&amp;#x2F;abs&amp;#x2F;1403.6681&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;arxiv.org&amp;#x2F;abs&amp;#x2F;1403.6681&lt;/a&gt;</text></comment>