It turns out that the magical world behind the looking-glass portrayed in Lewis Carroll’s novel about Alice is real – it has been discovered and described by physicists. So how do we find a way in?
Schrödinger's Cat was proposed by Erwin Schrödinger, the infamous thought experiment in which a cat in a box was both alive and dead simultaneously illustrating a quantum phenomenon known as superposition. In 2013, Yakir Aharonov and his co-authors conceived of an experiment suggesting that a particle can be separated from its property. They called the effect a "Quantum Cheshire Cat" that has been experimentally verified in the succeeding year. The name Quantum Cheshire Cat is inspired from a fanciful character of the Cheshire Cat in "\textit{Alice's Adventures in Wonderland"} a novel written by Lewis Carroll where the grin of cat is found without a cat. An important question arises here. Once the grin of the Cheshire Cat is separated, is there any correlation still left between the grin and the cat? To answer the question we propose a thought experiment in which Quantum Cheshire Cat is also a Schrödinger's Cat existing in superposition of happy(smiling) and sad(frowning) states. We name this cat as a "Quantum Mona Lisa Cat" for the reason that historically it is presumed that Mona Lisa's portrait contains both characteristics of happy(smiling) and sad(frowning) and either is observed depending upon the mood of the observer. We show that property separated from particle behave as "Quantum Mona Lisa Cat".
In Alice's Adventures in Wonderland by Lewis Carroll, mischievous grin of a Cheshire cat is sometimes dis-embodied from her body. Quantum theory allows such a counterintuitive phenomenon, known as the quantum Cheshire cat effect [1], to happen for a pre- and post-selected (PPS) system. While observing the quantum Cheshire cat, the physical property and the carrier's location should be weakly probed with a measuring device to leave the quantum state with negligible disturbance. To date, experimental observations of the quantum Cheshire cat effect have been realized with a single neutron as well as with a single photon [2, 3]. However, their observations relied on weakly disturbing elements instead of a true weak measuring device. In this work, we report the experimental observation of the quantum Cheshire cat effect with a weak measuring device. To investigate the quantum Cheshire cat effect, we employ a photon pair generated by spontaneous parametric down conversion (SPDC). The elements of quantum Cheshire cat, namely the body (photon) and the grin (polarization), are indirectly probed with a quantum pointer using another single photon, where both the body and the grin are weakly measured without destroying the photon itself.
“Meet Henry Bar, a physicist and … quantum superhero.” The title The Quantum Matrix refers to a central concept in quantum physics, but also (allegorically) to our enigmatic world. In this book, Henry Bar, physicist and the first quantum superhero, guides the reader through the amazing quantum world. Henry’s hair-raising adventures in his perilous struggle for quantum coherence are graphically depicted by comics and thoroughly explained to the lay reader. Behind each adventure lies a key concept in quantum physics. These concepts range from the basic quantum coherence and entanglement through tunneling and the recently discovered quantum decoherence control, to the principles of the emerging technologies of quantum communication and computing. The explanations of the concepts are popular, but nonetheless rigorous and detailed, and are followed by their broader context, their historic perspective, up-to-date status and forthcoming developments. Finally, thought-provoking philosophical and cultural implications of these concepts are discussed. The mathematical appendices of all chapters cover, in a straightforward manner, the core aspects of quantum physics at the level of a university introductory course. The Quantum Matrix presents an entertaining, popular yet comprehensive picture of quantum physics. It can be read as a light-hearted illustrated tale, a philosophical treatise or a textbook. Either way, the book lets the reader delve deeply into the wondrous quantum world from diverse perspectives and obtain glimpses into the quantum technologies that are about to reshape our lives. May the reader’s voyage through the quantum world charted by this book be both pleasant and rewarding.