Quantum Mechanics

Julian Schwinger had plans to write a textbook on quantum mechanics since the 1950s when he was teaching the subject at Harvard University regularly. * t Roger Newton remembers: [A] group of us (Stanley Deser, Dick Arnowitt, Chuck Zemach, Paul Martin and I forgot who else) wrote up lecture notes on his Quantum Mechanics course but he never wanted them published because he "e;had not yet found the perfect way to do quantum mechanics. "e; The only text of those days that got published eventually - following a sug- gestion by, and with the help of, Robert Kohler:!: - were the notes to the lectures that Schwinger presented at Les Houches in 1955. The book was reissued in 1991, with this Special Preface by Schwinger [3]: The first two chapters of this book are devoted to Quantum Kine- matics. In 1985 I had the opportunity to review that development in connection with the celebration of the 100th anniversary of Hermann Weyl's birthday. [ . . . ] In presenting my lecture [4] I felt the need to alter only one thing: the notation. Lest one think this rather triv- ial, recall that the ultimate abandonment, early in the 19th century, of Newton's method of fluxions in favor of the Leibnizian calculus, stemmed from the greater flexibility of the latter's notation.