Record-Breaking Quantum Superposition Experiment

🔷 How a Single Photon Can Be in Two Places at Once 🔷 Quantum physics just gave us another mind-bender — and it’s backed by math. 📖 Based on: Fukuda et al., 2025 — arXiv:2505.00336 📰 New Scientist dubbed it: “A photon caught in two places at once could destroy the multiverse.” Ever wondered whether a single photon can “exist” in both arms of an interferometer — and still produce perfect interference? ➡ The answer is yes, if you use a tool from quantum foundations: weak measurement theory. Here's how it works: ⚙️ ① Prepare a Superposition A photon enters a Mach–Zehnder interferometer through a beam splitter: |ψ⟩ = (|1⟩ + |2⟩) / √2, with polarization |H⟩ |1⟩: photon in arm 1 |2⟩: photon in arm 2 The photon is in both arms, but we haven’t measured which. 🌀 ② Weak Probes Gently "Tag" Each Arm In each arm, we apply a tiny polarization rotation ε (a weak wave plate). It slightly rotates the polarization only if the photon passes through that arm: U_j = exp(−iε σ_y P_j), ε ≪ 1 σ_y: acts on polarization P_j: projects onto arm j Net effect: polarization is nudged without collapsing the state. 🧪 ③ Post-Select on Interference We only look at events where the photon exits the constructive-interference port. The state after post-selection: |ψ_f⟩ = (|1⟩ + |2⟩)/√2 ⊗ |H⟩ ➡ The system interferes perfectly — proving the photon’s superposition was preserved. 📉 ④ Measure Weak Values: Half in Each Arm! Now compute the weak value of presence in arm j: (P_j)_w = ⟨ψ_f| P_j |ψ_i⟩ / ⟨ψ_f | ψ_i⟩ = 1/2 ➡ This tells us: the photon was “half-present” in each arm. You didn’t collapse the wavefunction — but still got a measurable result. 🎯 ⑤ Detect Polarization Shift Each ε-rotation affects the final polarization slightly. We observe: ⟨σ_x⟩ ≈ 2ε × Re[(P_j)_w] = ε ➡ Total rotation = ε, i.e., ½ + ½ from both arms. This is physical proof that a single photon acts in both places. 🧠 ⑥ Implications for Quantum Foundations Standard View: Any “which-path” info collapses interference. Weak Measurement View: You can extract partial presence without collapse. Many-Worlds Challenge: A single photon leaves real imprints in both arms — hard to reconcile with full-branch separation. 🔑 Key Takeaways ✅ Superposition is real and detectable ✅ Weak values are measurable, not abstract ✅ Interference survives gentle probing ✅ Quantum reality may be more delocalized than classical thinking allows 💡 This has profound implications for quantum sensing, precision metrology, and the future of quantum information. 🧭 The question is no longer if a particle can be in two places — It’s how gently you have to ask to prove it. #QuantumPhysics #Photon #Interferometry #WeakMeasurement #QuantumInterpretation #Fukuda2025 #ManyWorlds #Metrology #QuantumTechnology #Physics

Quantum Surprise: Schrödinger’s Cat Survives at Near-Boiling Temperatures Introduction: Rewriting the Rules of Quantum Thermodynamics Quantum effects are notoriously fragile and have traditionally been observed only at ultra-cold, near-absolute-zero temperatures. But in a groundbreaking study, researchers have demonstrated for the first time that quantum states—specifically Schrödinger cat states—can persist at significantly higher temperatures. This breakthrough challenges long-held assumptions about thermal limitations in quantum physics and could open the door to more practical quantum technologies. Key Breakthroughs in the Study • Hot Schrödinger Cat States Created • Researchers successfully created and measured quantum cat states at 1.8 Kelvin (-271.3°C)—a stark contrast to the milli-Kelvin ranges usually required. • While still extremely cold by everyday standards, this temperature is orders of magnitude higher than typical quantum experiments. • Quantum Effects Withstand Heat • The study demonstrated quantum superposition and interference—the hallmarks of quantum mechanics—persisting at much warmer conditions. • The experiment defies conventional wisdom that rising temperatures inevitably destroy delicate quantum states. • Team and Validation • Led by physicists at the University of Innsbruck, including PhD student Thomas Agrenius, the team confirmed their findings with detailed measurements. • Their results were met with surprise and skepticism from the quantum community until rigorous data validated the findings. • Why Schrödinger’s Cat Matters • The “cat” in Schrödinger’s famous thought experiment symbolizes a quantum object being in two states at once—alive and dead—until observed. • Real-world replication of such superpositions, especially at higher temperatures, is crucial for scalable quantum computing and sensing technologies. Why This Matters: Unlocking More Practical Quantum Technologies This discovery dramatically broadens the potential for real-world applications of quantum mechanics. If quantum effects can persist at less extreme temperatures, the infrastructure required for quantum computers, sensors, and communication systems could become significantly more practical and affordable. Overcoming the “cold barrier” has long been seen as essential for commercializing quantum devices. By proving that Schrödinger’s cat can survive in the heat, researchers have taken a bold step toward making quantum technology more robust, accessible, and ready for integration into everyday use.

Physicists have created "hotter" Schrödinger cat states, which are quantum states that exist in multiple conditions at once, by maintaining quantum superpositions at higher temperatures than previously possible. This breakthrough, achieved at temperatures up to 1.8 Kelvin—or about 60 times hotter than the previous record—demonstrates that quantum phenomena can persist in warmer, less ideal conditions. This could significantly lower the cost and complexity of quantum technology, making quantum computers more practical and easier to build. The breakthrough What they are: A "Schrödinger cat state" is a quantum system in a superposition of two distinct states simultaneously, a concept named after the famous thought experiment. The challenge: Normally, these states are so fragile they must be maintained at temperatures near absolute zero to prevent the superposition from collapsing. The new achievement: A research team created these states at temperatures up to 1.8 Kelvin, which is much warmer than the previous limit. How they did it: They adapted experimental protocols to generate and maintain the quantum states at these higher temperatures, using a specialized microwave resonator and carefully designed microwave pulses. Significance for quantum technology Reduced costs: The ability to perform experiments at higher temperatures means less need for extremely expensive and complex cooling equipment. New possibilities: It shows that quantum interference can persist even in less-than-ideal conditions, opening new opportunities for quantum computing and other technologies. More practical quantum computers: By proving that quantum effects are more robust, this research moves quantum technology closer to practical applications that could run in less controlled environments. More info: https://lnkd.in/e8YfDxyb