First up, we talk to Andrew Jordan of Rochester University about recent experiments that allow you to track and steer Schrodinger's metaphorical cat (or in this case a superconducting "transmon") between life and death, while it is locked in a box. The technique could be used to create a new kind of quantum control.

Other animals featuring in the main podcast are quantum pigeons. FQXi member Jeff Tollaksen chats about his theoretical analysis that suggests that there is a new type of quantum correlation that's even spookier than those we've come to know and love. We're used to talking about quantum entanglement, which continues to link two or more particles that have been specially prepared together, no matter how far apart they are separated. But Tollaksen and his colleagues have calculated that quantum particles can become united without having to ever have been in contact. And he illustrates this by talking about vanishing pigeons!

Both of these items described by Jordan and Tollaksen are based on pioneering theoretical work on "weak measurements" in the 1960s by FQXi member Yakir Aharonov and colleagues. These allow experimenters to measure some properties of quantum systems, without destroying them. You can read more about that program in the article, "The Destiny of the Universe" by Julie Rehmeyer.

That research program has also lead to the idea that it is possible to create what Tollaksen dubs a "Quantum Cheshire Cat." Just as the cat in Alice in Wonderland managed to slowly vanish leaving behind a grin without a cat, physicists have recently carried out experiments in which a neutron has been separated from its properties. Tollaksen spoke to me about these tests too, and you can hear that as a podcast extra on the website, but note that it is not in the main podcast. (The image above, by Leon Filter, appears in the team's paper in Nature Communications. Thank you to Gina Parry for suggesting a forum post based on this piece of research.)

We have also included some non-animal items too. For cosmology fans, and those hankering for a resolution of the black hole information paradox, check out the interview with FQXi's Carlo Rovelli. His latest analysis with Hal Haggard, based on the theory of Loop Quantum Gravity, predicts that when black holes die, they explode into white holes, spewing all the matter that they swallowed back out ...]]>

This year, we're doing something a bit different with the announcement of the big winners. We're inviting

The event: The FQXi Essay Contest Award Ceremony 2014

The time: Thursday 21st August, 1pm EDT

The place: Here

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This is also your chance to

So congratulations to our panellists, who between them have won the top 3 prizes. They are listed here in

Please post your questions and comments below (or tweet them to @FQXi).

We've also been busy announcing the names of our six 3rd place winners ($2,000), five 4th place winners ($1,000) and two special prize winners ($1,000) on twitter and Facebook. You can check out the list of the winners who have been revealed so far here. Congratulations to each of them for providing some thought-provoking reading matter.]]>

Quantum systems are associated with states which encode the statistics of future possible measurements. The collection of such states may be represented as a geometric shape. In the smallest possible quantum systems, single qubits (quantum bits), this shape is a sphere, called the Bloch sphere.

For example, think about a property of a qubit, such as its position: the qubit could be associated with two possible positions, A and B, say, or it can be in a fuzzy superposition where it exists in both of these mutually incompatible states simultaneously, before being observed. If it's in a superposition then although experimenters cannot know with certainty what position they will find it in when they make a measurement, they will have some sense of the probability of getting a certain outcome. The Bloch sphere helps to visualise this odd feature and the probabilistic nature of quantum mechanics. In the example, a vector pointing to the north pole of the sphere could represent position A, while the south pole represents position B. (In a classical system, this would represent the only two options available for a binary digit, or bit, to access). However, a qubit can also be represented by a vector pointing elsewhere on the surface of the sphere, corresponding to the fuzzy in-between states.

The maximal state space conceivable would actually be the cube outside of the sphere, as shown in figure 2. The quantum state space is the sphere, but if there were no uncertainty principle all states in the outer cube could be allowed. In this case certain measurements could all have predictable outcomes at the same time, in violation of the quantum uncertainty principle.

One may ask why quantum theory is restricted to the sphere, and accordingly to having the uncertainty principle.

We came across an intriguing answer when thinking about how the cube state space would handle an interferometer. In an interferometer the particle or photon is firstly placed in a superposition of being in two places and then operations are d...]]>