اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدMaria Krawczyk: friend and physicist
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Rohini M. Godbole
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With this note, we remember our friend Maria Krawczyk, who passed away this year, on May 24th. We briefly outline some of her physics interests and main accomplishments, and her great human and moral qualities.
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In the history of the discovery tools of last century particle physics, central stage is taken by elementary particle accelerators and in particular by colliders. In their start and early development, a major role was played by the Austrian born Brun
o Touschek, who proposed and built the first electron positron collider, AdA, in Italy, in 1960. In this note, we present a period of Touscheks life barely explored in the literature, namely the five years he spent at University of Glasgow, first to obtain his doctorate in 1949 and then as a lecturer. We shall highlight his formation as a theoretical physicist, his contacts and correspondence with Werner Heisenberg in Gottingen and Max Born in Edinburgh, as well as his close involvement with colleagues intent on building modern particle accelerators in Glasgow, Malvern, Manchester and Birmingham. We shall discuss how the Fuchs affair, which unraveled in early 1950, may have influenced his decision to leave the UK, and how contacts with the Italian physicist Bruno Ferretti led Touschek to join the Guglielmo Marconi Physics Institute of University of Rome in January 1953.
John Couch Adams predicted the location of Neptune in the sky, calculated the expectation of the change in the mean motion of the Moon due to the Earths pull, and determined the origin and the orbit of the Leonids meteor shower which had puzzled astr
onomers for almost a thousand years. With his achievements Adams can be compared with his good friend George Stokes. Not only were they born in the same year, but were also both senior wranglers, received the Smiths Prizes and Copley medals, lived, thought and researched at Pembroke College, and shared an appreciation of Newton. On the other hand, Adams prediction of Neptunes location had absolutely no influence on its discovery in Berlin. His lunar theory did not offer a physical explanation for the Moons motion. The origin of the Leonids was explained by others before him. Adams refused a knighthood and an appointment as Astronomer Royal. He was reluctant and slow to publish, but loved to derive the values of logarithms to 263 decimal places. The maths and calculations at which he so excelled mark one of the high points of celestial mechanics, but are rarely taught nowadays in undergraduate courses. The differences and similarities between Adams and Stokes could not be more striking. This volume attests to the lasting legacy of Stokes scientific work. What is then Adams legacy? In this contribution I will outline Adams life, instances when Stokes and Adams lives touched the most, his scientific achievements and a usually overlooked legacy: female higher education and support of a woman astronomer.
The measurement problem is seen as an ambiguity of quantum mechanics, or, beyond that, as a contradiction within the theory: Quantum mechanics offers two conflicting descriptions of the Wigners-friend experiment. As we argue in this note there are, h
owever, obstacles from within quantum mechanics and regarding our perspective onto doing physics towards fully describing a measurement. We conclude that the ability to exhaustively describe a measurement is an assumption necessary for the common framing of the measurement problem and ensuing suggested solutions.
In a joint paper Jeff Bub and Itamar Pitowski argued that the quantum state represents `the credence function of a rational agent [...] who is updating probabilities on the basis of events that occur. In the famous thought experiment designed by Wign
er, Wigners friend performs a measurement in an isolated laboratory which in turn is measured by Wigner. Here we consider Wigners friend as a rational agent and ask what her `credence function is. We find experimental situations in which the friend can convince herself that updating the probabilities on the basis of events that happen solely inside her laboratory is not rational and that conditioning needs to be extended to the information that is available outside of her laboratory. Since the latter can be transmitted into her laboratory, we conclude that the friend is entitled to employ Wigners perspective on quantum theory when making predictions about the measurements performed on the entire laboratory, in addition to her own perspective, when making predictions about the measurements performed inside the laboratory.
Wigners friend thought experiment is intended to reveal the inherent tension between unitary evolution and measurement collapse. On the basis of Wigners friend experiment, Brukner derives a no-go theorem for observer-independent facts. We construct a
n extended Wigners friend scenario including three laboratories, namely, Alices laboratory, Bobs laboratory and Charlies laboratory, where Alice, Bob and Charlie are standing outside the laboratories while their friends are placed inside their own laboratories. We consider quantum simulation via Q# quantum programming and also realize the primary quantum circuits using IBM quantum computers. Then, we calculate the probabilities and corresponding statistical uncertainties. It has been shown that the results of quantum simulation are clearly consistent with theoretical values, while it has a slightly higher error rates for the experimental results of quantum computers mainly because of a series of quantum gates, especially CNOT gates.
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