<story><title>Sustained, high-fidelity quantum teleportation</title><url>https://news.fnal.gov/2020/12/fermilab-and-partners-achieve-sustained-high-fidelity-quantum-teleportation/</url></story><parent_chain><item><author>junon</author><text>This makes zero sense. If the information must be conveyed classically anyway, what&amp;#x27;s the point?</text></item><item><author>pontus</author><text>You entangle two systems but in order to actually complete the teleportation you need to measure one system and then convey the outcome of that measurement to the other party. This information is needed by the second party in order for them to be able to correctly collapse the state of their system into one that is identical to the original system being teleported. The information that the first party must convey to the receiving party must be sent in a classical way (e.g. a phone call).</text></item><item><author>sabellito</author><text>I&amp;#x27;m confused, as I&amp;#x27;m an enthusiast but definitely no physicist.&lt;p&gt;The article states that quantum information is being teleported via entanglement. However, it was my understanding that one cannot transfer information in such a way as the &amp;quot;information&amp;quot; is only revealed when interacting with the particle.&lt;p&gt;Could someone perhaps clarify what&amp;#x27;s going on?</text></item></parent_chain><comment><author>pontus</author><text>Great question! This gets to the heart of why quantum teleportation has any value at all.&lt;p&gt;So, before QM there was already a sense in which you could teleport an object: simply measure its state perfectly and send that information to another location and have them reconstruct that state particle by particle. In principle the new system would be indistinguishable from the original system and you could claim that you&amp;#x27;ve teleported it. Now, with the discovery of quantum mechanics, this process no longer works because there is no way to measure the complete state of a quantum system. For example, you could measure the position of each particle to arbitrary accuracy or you can measure the speed of every particle to arbitrary position, but you can&amp;#x27;t do both (Heisenberg&amp;#x27;s uncertainty principle). So, it would seem like one could not construct a perfect replica of a quantum system in a new location by measuring its state in the original position.&lt;p&gt;The cleverness of quantum teleportation is that you use entanglement to sort of short circuit this limitation. You let entanglement do the heavy lifting to sort of &amp;quot;copy&amp;quot; the state from one location to another and then perform a measurement in the original location to uncover just enough information so that the person in the second location can manipulate its system to reconstruct the original state.&lt;p&gt;It&amp;#x27;s sort of like reconstructing the state without actually knowing what that state is.&lt;p&gt;Now, an interesting side effect of the quantum version is that the first measurement of the original system is necessarily destructive. As such, it&amp;#x27;s not like you&amp;#x27;ll end up with two copies of the same thing (which is what would happen in the classical version) so there&amp;#x27;s no discussion necessary around the distinction between teleportation and cloning. Classically you&amp;#x27;d be cloning the system but quantum mechanically you&amp;#x27;d really truly be teleporting it (in fact, there&amp;#x27;s a result in quantum mechanics called &amp;quot;the no cloning theorem&amp;quot; that proves that cloning in QM is impossible).</text></comment>
<story><title>Sustained, high-fidelity quantum teleportation</title><url>https://news.fnal.gov/2020/12/fermilab-and-partners-achieve-sustained-high-fidelity-quantum-teleportation/</url></story><parent_chain><item><author>junon</author><text>This makes zero sense. If the information must be conveyed classically anyway, what&amp;#x27;s the point?</text></item><item><author>pontus</author><text>You entangle two systems but in order to actually complete the teleportation you need to measure one system and then convey the outcome of that measurement to the other party. This information is needed by the second party in order for them to be able to correctly collapse the state of their system into one that is identical to the original system being teleported. The information that the first party must convey to the receiving party must be sent in a classical way (e.g. a phone call).</text></item><item><author>sabellito</author><text>I&amp;#x27;m confused, as I&amp;#x27;m an enthusiast but definitely no physicist.&lt;p&gt;The article states that quantum information is being teleported via entanglement. However, it was my understanding that one cannot transfer information in such a way as the &amp;quot;information&amp;quot; is only revealed when interacting with the particle.&lt;p&gt;Could someone perhaps clarify what&amp;#x27;s going on?</text></item></parent_chain><comment><author>abdullahkhalids</author><text>Physical qubits are much more sensitive to transmission noise than physical bits. If you want to transmit qubits, teleportation allows you to do it with higher fidelity than by physical transmission.&lt;p&gt;Why do you want to transmit qubits? For various emerging quantum information technologies, each with different potential economic impact.</text></comment>