Matt Strassler
@mattstrassler.bsky.social
Theoretical physicist (particle physics, string theory, black holes), semi-retired professor, writer (author of the popular science book "Waves in an Impossible Sea"), amateur musician, and activist for founding public policy on facts and logic
⚛️🧪Is Superposition Really an "OR"? If a quantum system is in a superposition state "A+B", does it mean that "A AND B" are true, or that "A OR B " is true, or something else? An example of why ordinary language is not easily applied to #quantum physics. profmattstrassler.com/2025/04/14/i...
Is Superposition Really an "OR"?
If a quantum system is in a superposition state "A+B", does it mean that "A AND B" are true, or that "A OR B " is true, or something else?
profmattstrassler.com
April 14, 2025 at 12:48 PM
⚛️🧪Is Superposition Really an "OR"? If a quantum system is in a superposition state "A+B", does it mean that "A AND B" are true, or that "A OR B " is true, or something else? An example of why ordinary language is not easily applied to #quantum physics. profmattstrassler.com/2025/04/14/i...
⚛️🧪In the #quantum double slit experiment, the famous #interference pattern disappears if we measure which slit the particle went through. Why does it disappear? It's often described in vague, mystical terms, but in fact it's conceptually straightforward: profmattstrassler.com/2025/04/03/d...
Double Slit: Why Measurement Destroys the Interference Pattern
Measurement eliminates the interference pattern in the quantum double slit experiment. This fact, despite its reputation, is conceptually straightforward.
profmattstrassler.com
April 3, 2025 at 12:41 PM
⚛️🧪In the #quantum double slit experiment, the famous #interference pattern disappears if we measure which slit the particle went through. Why does it disappear? It's often described in vague, mystical terms, but in fact it's conceptually straightforward: profmattstrassler.com/2025/04/03/d...
⚛️The interference of water waves happens somewhere -- wherever the waves are, obviously. But #quantum interference happens... nowhere. If you try to say exactly where two #entangled particles interfere, you will find yourself lost in space. profmattstrassler.com/2025/03/31/q...
March 31, 2025 at 3:56 PM
⚛️The interference of water waves happens somewhere -- wherever the waves are, obviously. But #quantum interference happens... nowhere. If you try to say exactly where two #entangled particles interfere, you will find yourself lost in space. profmattstrassler.com/2025/03/31/q...
⚛️🧪If particles are #entangled, observing #quantum interference effects can be subtle, often requiring measuring multiple particles. As a result, quantum interference cannot generally be located in a specific place, unlike interference of e.g. water waves. profmattstrassler.com/2025/03/31/q...
March 31, 2025 at 12:43 PM
⚛️🧪If particles are #entangled, observing #quantum interference effects can be subtle, often requiring measuring multiple particles. As a result, quantum interference cannot generally be located in a specific place, unlike interference of e.g. water waves. profmattstrassler.com/2025/03/31/q...
⚛️🧪In the #quantum double-slit experiment, it's natural to ask, "where does the interference occur?" But it's a dicey question: an answer is only possible in special situations, as when the particles are independent (i.e. their behavior is "uncorrelated".)
profmattstrassler.com/2025/03/28/q...
profmattstrassler.com/2025/03/28/q...
Quantum Interference 4: Independence and Correlation
It's a natural question: "where does quantum interference occur?" But it rarely has an answer, unless e.g. 2 particles are truly independent (uncorrelated.)
profmattstrassler.com
March 28, 2025 at 1:25 PM
⚛️🧪In the #quantum double-slit experiment, it's natural to ask, "where does the interference occur?" But it's a dicey question: an answer is only possible in special situations, as when the particles are independent (i.e. their behavior is "uncorrelated".)
profmattstrassler.com/2025/03/28/q...
profmattstrassler.com/2025/03/28/q...
⚛️🧪The #quantum double-slit experiment shows an interference pattern; but what is interfering with what? Today I explore examples that show how seemingly minor changes can eliminate interference, and why locating the interference in space is ... problematic. profmattstrassler.com/2025/03/26/q...
Quantum Interference 3: What Is Interfering?
What interferes with what in the quantum double-slit experiment? Minor changes can eliminate interference, & locating the interference in space is misguided
profmattstrassler.com
March 26, 2025 at 12:37 PM
⚛️🧪The #quantum double-slit experiment shows an interference pattern; but what is interfering with what? Today I explore examples that show how seemingly minor changes can eliminate interference, and why locating the interference in space is ... problematic. profmattstrassler.com/2025/03/26/q...
Reposted by Matt Strassler
"Nobody really knows what the elementary laws of nature are like yet; there are still too many unknowns." Still,
@mattstrassler.bsky.social's astounding book Waves in an Impossible Sea is for me a refuge from the constant barrage of chaos and danger surrounding us right now.
@mattstrassler.bsky.social's astounding book Waves in an Impossible Sea is for me a refuge from the constant barrage of chaos and danger surrounding us right now.
March 20, 2025 at 4:55 PM
"Nobody really knows what the elementary laws of nature are like yet; there are still too many unknowns." Still,
@mattstrassler.bsky.social's astounding book Waves in an Impossible Sea is for me a refuge from the constant barrage of chaos and danger surrounding us right now.
@mattstrassler.bsky.social's astounding book Waves in an Impossible Sea is for me a refuge from the constant barrage of chaos and danger surrounding us right now.
⚛️🧪Here are 10 examples of simple one- or two-particle systems in #quantum superpositions. Some show quantum interference (like double-slit), others don't. Do you see the pattern that distinguishes the two groups? Why & when does interference happen (...or not)? profmattstrassler.com/2025/03/20/q...
Quantum Interference 2: When Does It Happen?
Here are 9 examples of simple 2-particle systems in quantum superpositions, some with interference, some without. What pattern distinguishes the 2 sets?
profmattstrassler.com
March 20, 2025 at 12:46 PM
⚛️🧪Here are 10 examples of simple one- or two-particle systems in #quantum superpositions. Some show quantum interference (like double-slit), others don't. Do you see the pattern that distinguishes the two groups? Why & when does interference happen (...or not)? profmattstrassler.com/2025/03/20/q...
⚛️🧪In yesterday's post, I showed a simple example where one particle can give the same #quantum interference as in the double-slit experiment. Then I posed a puzzle about two particles, which has generated a debate in the comments. Can you solve the riddle? profmattstrassler.com/blog/
Of Particular Significance
Conversations About Science with Theoretical Physicist Matt Strassler
profmattstrassler.com
March 19, 2025 at 10:06 PM
⚛️🧪In yesterday's post, I showed a simple example where one particle can give the same #quantum interference as in the double-slit experiment. Then I posed a puzzle about two particles, which has generated a debate in the comments. Can you solve the riddle? profmattstrassler.com/blog/
⚛️🧪A super-simple example of #quantum #interference, in which an interference pattern emerges #particle by particle (as in the double slit expt). It frames a question clearly: is the particle interfering with itself, or is it not? Answer to follow. profmattstrassler.com/2025/03/18/q...
Quantum Interference 1: A Simple Example
An example of quantum interference so simple that important questions about the origin of the interference can be investigated explicitly.
profmattstrassler.com
March 18, 2025 at 12:25 PM
⚛️🧪A super-simple example of #quantum #interference, in which an interference pattern emerges #particle by particle (as in the double slit expt). It frames a question clearly: is the particle interfering with itself, or is it not? Answer to follow. profmattstrassler.com/2025/03/18/q...
⚛️🧪I've been interviewed on the Blackbird #Physics YouTube channel by UMich. grad student & LHC physicist Ibrahim Chahrour. The interview, aimed largely at physics undergrad & grad students, covers mass, fields, #particles & the #Higgs boson. www.youtube.com/watch?v=ly15...
How the Higgs ACTUALLY gives particles Mass - Matt Strassler | Blackbirdphys #3
YouTube video by blackbirdphys
www.youtube.com
March 17, 2025 at 12:46 PM
⚛️🧪I've been interviewed on the Blackbird #Physics YouTube channel by UMich. grad student & LHC physicist Ibrahim Chahrour. The interview, aimed largely at physics undergrad & grad students, covers mass, fields, #particles & the #Higgs boson. www.youtube.com/watch?v=ly15...
Reposted by Matt Strassler
I was curious about this so I corrected the scale.
March 14, 2025 at 6:29 PM
I was curious about this so I corrected the scale.
🔭 The eclipsed Moon from Earth, and the eclipsing Earth from the Moon spaceweathergallery2.com/indiv_upload...
Blue Ghost And Earth Comparison Of The Total Solar Eclipse
spaceweathergallery2.com
March 14, 2025 at 5:49 PM
🔭 The eclipsed Moon from Earth, and the eclipsing Earth from the Moon spaceweathergallery2.com/indiv_upload...
⚛️🧪To make sense of the #quantum double slit experiment, one must first learn this strange lesson: in 1920s quantum physics, the interference arises *neither* from particles moving through both slits *nor* from a wave function moving through both slits. profmattstrassler.com/2025/03/13/d...
Did the Particle Go Through the Two Slits, or Did the Wave Function?
In the quantum double-slit experiment, did the particle go through the slits or did the wave function? 1920's quantum physics has a simple answer: "NO".
profmattstrassler.com
March 13, 2025 at 2:49 PM
⚛️🧪To make sense of the #quantum double slit experiment, one must first learn this strange lesson: in 1920s quantum physics, the interference arises *neither* from particles moving through both slits *nor* from a wave function moving through both slits. profmattstrassler.com/2025/03/13/d...
Reposted by Matt Strassler
This is another one that is a "must read" to entertain myself this gloomy/cloudy afternoon... ❤️
⚛️🧪What is a measurement? A tricky question, especially in our #quantum world. As a first step, here's a way to think about it: a sketch of a simple measurement device in a simple quantum setting, one that we can use in future in more complex situations. profmattstrassler.com/2025/02/27/w...
What Is a Measurement?
A measurement requires a device with some important properties that I describe. I then focus on a simple intuitive quantum measurement device
profmattstrassler.com
February 27, 2025 at 9:40 PM
This is another one that is a "must read" to entertain myself this gloomy/cloudy afternoon... ❤️
⚛️🧪Do wave functions describing #quantum objects actually "collapse" (i.e., suddenly change shape and lose pieces) when those objects are measured? Here's how to think about the issue clearly, without getting mired in illogical conundrums and bad arguments profmattstrassler.com/2025/03/10/d...
Do Quantum Wave Functions Collapse?
Do wave functions "collapse" when the objects they describe are measured? Here's how to think about the issue clearly while avoiding illogical arguments
profmattstrassler.com
March 10, 2025 at 12:28 PM
⚛️🧪Do wave functions describing #quantum objects actually "collapse" (i.e., suddenly change shape and lose pieces) when those objects are measured? Here's how to think about the issue clearly, without getting mired in illogical conundrums and bad arguments profmattstrassler.com/2025/03/10/d...
⚛️🧪A #quantum superposition, in which a wave function contains 2 possibilities simultaneously, does not mean that both possibilities occur. It means that one *or* the other may occur; e.g. a quantum particle cannot be observed to go in 2 directions at once. profmattstrassler.com/2025/03/06/c...
Can a Quantum Particle Move in Two Directions at Once?
A wave function superposition shows a quantum particle moving in either direction, but the particle itself can only be moving in one direction OR the other.
profmattstrassler.com
March 6, 2025 at 1:28 PM
⚛️🧪A #quantum superposition, in which a wave function contains 2 possibilities simultaneously, does not mean that both possibilities occur. It means that one *or* the other may occur; e.g. a quantum particle cannot be observed to go in 2 directions at once. profmattstrassler.com/2025/03/06/c...
#quantum #physics: In measurements of ultra-microscopic objects, the resulting measurement evidence is fragile & easily lost. How do experimental physicists preserve the evidence quickly, before it's too late? profmattstrassler.com/2025/03/03/m...
Making a Measurement Permanent
Evidence in measurements of microscopic particles is fragile & easily lost. Experimental physicists must preserve it quickly, using amplification.
profmattstrassler.com
March 3, 2025 at 1:28 PM
#quantum #physics: In measurements of ultra-microscopic objects, the resulting measurement evidence is fragile & easily lost. How do experimental physicists preserve the evidence quickly, before it's too late? profmattstrassler.com/2025/03/03/m...
⚛️🧪What is a measurement? A tricky question, especially in our #quantum world. As a first step, here's a way to think about it: a sketch of a simple measurement device in a simple quantum setting, one that we can use in future in more complex situations. profmattstrassler.com/2025/02/27/w...
What Is a Measurement?
A measurement requires a device with some important properties that I describe. I then focus on a simple intuitive quantum measurement device
profmattstrassler.com
February 27, 2025 at 1:41 PM
⚛️🧪What is a measurement? A tricky question, especially in our #quantum world. As a first step, here's a way to think about it: a sketch of a simple measurement device in a simple quantum setting, one that we can use in future in more complex situations. profmattstrassler.com/2025/02/27/w...
⚛️🧪A grasp of the "space of possibilities" [a.k.a. "configuration space"], and how to convert from it to the physical space we live in, is crucial in #physics, especially #quantum physics. I've added an article to help readers develop more intuition for it. profmattstrassler.com/articles-and...
Understanding the Space of Possibilities: An Example
To understand quantum physics, one must first understand the space of possibilities. Simple illustrative examples are covered here.
profmattstrassler.com
February 26, 2025 at 4:18 PM
⚛️🧪A grasp of the "space of possibilities" [a.k.a. "configuration space"], and how to convert from it to the physical space we live in, is crucial in #physics, especially #quantum physics. I've added an article to help readers develop more intuition for it. profmattstrassler.com/articles-and...
⚛️🧪#Wave functions in #quantum field theory are hard to visualize, & thus hard to understand. Today I address that problem, partially depicting the wave function for a field's vacuum state (no "particles") & comparing it to that of a state with 1 "particle". profmattstrassler.com/2025/02/25/t...
The Particle and the "Particle" (Part 2)
I depict and explain the wave function for quantum field theory, for both the vacuum state (with zero particles) and for a state with one particle in it.
profmattstrassler.com
February 25, 2025 at 1:30 PM
⚛️🧪#Wave functions in #quantum field theory are hard to visualize, & thus hard to understand. Today I address that problem, partially depicting the wave function for a field's vacuum state (no "particles") & comparing it to that of a state with 1 "particle". profmattstrassler.com/2025/02/25/t...
⚛️🧪A #particle in 1920s #quantum #physics is a different beast from a "particle" in modern quantum field theory. This important distinction is inherently confusing. My aim this week is to bring a new level of pedagogical clarity to this tricky issue. profmattstrassler.com/2025/02/24/t...
The Particle and the "Particle" (Part 1)
A particle in 1920s quantum physics is a different beast from a "particle" in modern quantum field theory. I use novel methods to explain this tricky issue
profmattstrassler.com
February 24, 2025 at 1:55 PM
⚛️🧪A #particle in 1920s #quantum #physics is a different beast from a "particle" in modern quantum field theory. This important distinction is inherently confusing. My aim this week is to bring a new level of pedagogical clarity to this tricky issue. profmattstrassler.com/2025/02/24/t...
⚛️🧪From this example one can see (even more so in the 2-dimensional versions) that in 1920s quantum physics the double-slit interference pattern arises from interfering *possibilities*. [But caution: quantum field theory changes the perspective!] profmattstrassler.com/2025/02/20/c...
Can You Interpret This Quantum Wave Function?
A challenge for readers: here's a wave function evolving over time, as I described in a post earlier this week. Can you interpret what is happening here?
profmattstrassler.com
February 21, 2025 at 1:59 PM
⚛️🧪From this example one can see (even more so in the 2-dimensional versions) that in 1920s quantum physics the double-slit interference pattern arises from interfering *possibilities*. [But caution: quantum field theory changes the perspective!] profmattstrassler.com/2025/02/20/c...
⚛️🧪Yesterday I posted an animation of a #quantum wave function & asked readers to try to interpret it. Most people thought it shows 2 particles passing/colliding. In fact it shows just one particle in the midst of a disguised double-slit experiment! profmattstrassler.com/2025/02/21/i...
It was the Double Slit Experiment All Along!
The animation of a quantum wave function that I posted yesterday shows one particle, not two, and is closely related to the double slit experiment.
profmattstrassler.com
February 21, 2025 at 1:20 PM
⚛️🧪Yesterday I posted an animation of a #quantum wave function & asked readers to try to interpret it. Most people thought it shows 2 particles passing/colliding. In fact it shows just one particle in the midst of a disguised double-slit experiment! profmattstrassler.com/2025/02/21/i...
⚛️Most people -- even #physics students -- mistakenly think this #quantum wave function shows two #particles approaching each other and interfering with one another. But no. What, in fact, is it?
⚛️🧪A brain teaser for blog readers: here's an interesting #quantum #wave function evolving over time, shown 3 ways. Can you interpret what this wave function describes? Note the interference effects... what do they represent? Answers tomorrow. profmattstrassler.com/2025/02/20/c...
Can You Interpret This Quantum Wave Function?
A challenge for readers: here's a wave function evolving over time, as I described in a post earlier this week. Can you interpret what is happening here?
profmattstrassler.com
February 20, 2025 at 5:34 PM
⚛️Most people -- even #physics students -- mistakenly think this #quantum wave function shows two #particles approaching each other and interfering with one another. But no. What, in fact, is it?