# [PHYS G4021] Quantum Mechanics

- Departments: Physics
- Professors: Brian Greene and Erick Weinberg

Avoid. Unless you're a physics major, in which case you'll have to take this class and in all likelihood Prof. Weinberg will be teaching it, which makes your life doubly sad. Quantum mechanics is difficult, but where it could've been made interesting, Prof. Weinberg fails to do so on every count. He drones on in class, and places random equations on the board that he expects you to remember from last time (you won't), and gives little or no context for it. For the most part, he covers what's in the textbook, but not always, which can be frustrating since I found most of lectures impenetrable. First part of the semester leading up to the first midterm was alrightâ€”basically a recap of 2601 and covers the Schrodinger equation in 1 dimension with various potentials. Then, the class moves into grey areas when Prof. Weinberg spends a good chunk of time reviewing linear algebra in the most unenlightening way possible. This is where he lost my attention. The subsequent part of the course involved recasting quantum theory in the language of linear algebra, so I found myself playing catchup every lecture. One thing though, Prof. Weinberg curves pretty generously, and the class tends to have a HUGE spread in raw scores, so good or bad depending on who you are.

#### Workload:

Weekly problem sets (10%), 2 midterms (25%+25%), 1 final (40%).

I won't speak for others (I hear through the grapevine that some others liked the class less) but here's my impression:

Professor Weinberg loves the subject and is an enthusiastic teacher. He follows the textbook (Griffiths, Introduction to Quantum Mechanics) pretty closely so if you feel like it you can read along during the semester. Sometimes he'll deviate from Griffiths sequencing, but he usually announces this a lecture ahead of time.

If you're a real physics whiz, you probably don't have to come to class but my general observation from sitting in the front row all semester was that the top grades seemed to be clustered there -- Weinberg does add value with his lectures, unlike some physics profs. This semester, probably owing to the way the classroom was laid out, the class was pretty intimate. People would ask questions mid-lecture without raising their hands and would interrupt derivations to point out mistakes or ask about a technical point, and Professor Weinberg just rolled with it. I had fun with that, though I can understand if others found it distracting.

In general, the class's material isn't too difficult, but it gets harder as you go on. For the second month you should make sure you know your linear algebra, and for the final month you have to make sure you've got vector calculus down cold. On the hardest homework problems I found myself resorting to the solutions manual for hints (it's is available online if you look hard enough) but be warned: the homework isn't worth enough to be worth cheating on, and is at the same time crucial to picking up certain concepts that Weinberg uses the homework to teach that will appear on the far more valuable exams.

Up to the first midterm is stuff you'll probably already know, i.e. Schrodinger, infinite square well, harmonic oscillator, and a bit of knew stuff, i.e. delta-function well, and the free particle. The first midterm was very straightforward; four problems you could do if you had paid attention in class. I lost all my points on a dropped negative. The median was a 50 but it was pretty bimodal. A bunch of people clustered above 90 and a bunch clustered below 50.

The second midterm covers the matrix interpretation of quantum mechanics and all it implies, including a bit more on the free particle and delta well as well as the uncertainty principle and observables as eigenvalues. This midterm was a lot harder -- two fairly easy problems, two problems that were impossible if you didn't spot the trick (though in fairness the trick for each had fairly prominently figured on the homework) -- had a much tighter distribution, though the median was 50 again.

The last month of the class is quantum mechanics in 3 dimensions. The hydrogen atom, angular momentum, spin, etc. At this point (almost literally the day after the second midterm) I lost track of the class. I did vector calc as a freshman (senior now) and linear algebra in high school and that came back to bite me in the ass. I'm starting to get caught up now, but it wasn't fun. I'd say how I did on the final, but I'm writing this before it to avoid being biased by how I do on that.

#### Workload:

Weekly homework, 10% of the grade. Two midterms, each 25%. Final worth 40%. He said that the median grade was the A- cutoff last semester. I'm on track to be a bit north of the median, but not a lot.

So, G4022 is meant to be a class for physics majors. Instead, this class is a hybrid mesh of pure mathematics, physics and, albeit interesting, but not particularly useful for a physics majors, philosophy. Compared to how the physics department used to teach this course, this year's class had many holes in it, some of which were patched up in homeworks. Leaving the class to teach themselves half the material always poses risks that a student will not absorb the essentials of qm.

With the time remaining towards the end of the course, rather than cover topics the physics department typically teaches, such as the WKB approximation, the variational principle, along with other side topics that improve one's ability to perform calculations, the time was used to lecture about topics that were philosophical in nature. Among the topics were the measurement problem and many worlds philosophy, which, though interesting in their own way, are not helpful in teaching how to actually utilize qm.

Prof. Greene is rather charismatic, but this allows his ego to expand. To end this, physics majors be warned: You will have a major hole in your quantum basics, so be sure to read books and ask questions, but perhaps not ask Prof. Greene... you may just receive a "PBS Special" type of answer.

#### Workload:

Problem Set every week, reasonable. One midterm, one final. For the most part, all reasonable (also all made by his TA).

This professor deserves an unbiased culpa review that doesn't mention his fame.

Brian Greene is, in short, an incredible Professor, likely the greatest, most fun to listen to, enthusiastic professor I've ever had. He made quantum mechanics seem so easy, so crystal clear, that I felt as if I were taking high school level quantum. Lectures were fun and engaging, questions were encouraged and always answered without judgment. This led to some awkward moments when obvious or annoying questions were answered with as much detail as interesting questions, but made me feel eager not only to ask questions during class, but after class as well. As a note, this was a very tough semester for me as I had to deal with a personal loss, and when I emailed Professor Greene, he said that not only would I be allowed to hand in the next homework whenever I needed to, but he would personally tutor me on any lecture I missed, which I held him to.

The material itself was fairly basic quantum; no different than what is learned in the end of PHYS 2601, with more mathematical detail, and I'm pretty eager to figure out where he will take this course when more complex topics arise. It made me feel almost nervous that I wasn't learning enough physics. At other schools people complain that quantum is like the physics major organic chemistry, the sail-or-fail this-will-determine-whether-you-major-in-physics, but I can honestly say this quantum class was the easiest class of my fairly easy semester, if not the easiest physics class i've taken since high school.

Take it, you will be so happy you did.

#### Workload:

Weekly problem sets that simply walk you through the material and are often lifted directly from the textbook (and rarely take more than 2 hours), easy midterm that was graded harshly, difficult but not impossible final. Professor Greene said "If I could, I would give everyone an A." Duly noted, I did the minimum and still got an A-.

## Directory Data

Dept/Subj | Directory Course | Professor | Year | Semester | Time | Section |
---|---|---|---|---|---|---|

PHYS / PHYS | PHYS PHYS G4021: Quantum Mechanics I | Erick Weinberg | 2012 | Fall | TR / 10:10-11:25 AM | 1 |

PHYS / PHYS | PHYS PHYS G4021: Quantum Mechanics I | Alfred Mueller | 2010 | Fall | TR / 9:35-10:50 AM | 1 |

PHYS / PHYS | PHYS PHYS G4021: Quantum Mechanics I | Alfred Mueller | 2009 | Fall | TR / 9:35-10:50 AM | 1 |

PHYS / PHYS | PHYS PHYS G4021: Quantum Mechanics I | Giuseppina Cambareri, Alfred Mueller | 2008 | Fall | TR / 9:35-10:50 AM | 1 |

PHYS / PHYS | PHYS PHYS G4021: Quantum Mechanics I | Philip Kim | 2007 | Fall | TR / 9:35-10:50 AM | 1 |

PHYS / PHYS | PHYS PHYS G4021: Quantum Mechanics I | Philip Kim | 2006 | Fall | TR / 9:35-10:50 AM | 1 |

PHYS / PHYS | PHYS PHYS G4021: Quantum Mechanics I | Andrew Millis | 2004 | Fall | TR / 9:35-10:50 AM | 1 |

PHYS / PHYS | PHYS PHYS G4021: Quantum Mechanics I | Andrew Millis | 2003 | Fall | TR / 9:35-10:50 AM | 1 |

PHYS / PHYS | PHYS PHYS G4021: Quantum Mechanics I | Andrew Millis | 2002 | Fall | TR / 9:35-10:50 AM | 1 |

PHYS / PHYS | PHYS PHYS G4021: Quantum Mechanics I | Tony Heinz | 2001 | Fall | TR / 10:35-11:50 AM | 1 |