Techniques for Precise Quantum Particle Measurement

Today, Anthony Chen and I are posting a theory paper tackling a problem that I have been contemplating for a long time. Conventional wisdom suggests that quantum states are very fragile, like Schrodinger’s cat — if you look at the state, you destroy it. This poses a huge problem in using quantum computers for quantum simulation. Suppose you spend 3 hours meticulously preparing the ground state of some material or molecule on my quantum computer. If you measure the state, you get a few bits of information, but you destroy the state. In order to accurately predict physical phenomena, you may need to measure millions of times. In this paper, we show how to measure a ground state without causing any disturbance to the state. We call it “catalytic tomography”, since the quantum state is used but not consumed. How is this possible? The key is to use the parent Hamiltonian, and to apply energy filtering. As a consequence, ground states are not fragile like Schrodinger’s cats, but are robust like a classical memory, and readable like a book! Link to paper ➡️ https://lnkd.in/eBxydfwh

Physicists just found a loophole in Heisenberg’s famous rule. You can’t break Heisenberg’s uncertainty principle. But, as a team of Australian physicists just showed, you might be able to outsmart it. In quantum physics, Heisenberg’s principle says you can’t know a particle’s exact position and momentum at the same time. Measure one more precisely, and the other becomes more uncertain. It’s a fundamental rule that’s defined quantum mechanics for nearly a century. But researchers at the University of Sydney just found a clever workaround. Instead of measuring a particle’s absolute position and momentum, they measured something called modular position and momentum – which focuses only on small shifts within a repeating pattern. Think of it like measuring how far a marble has rolled since the last inch mark on a ruler, without worrying about which foot or yard you’re in. Using lasers and a single trapped ion, they created a "quantum grid" – a repeating pattern of wave peaks like the notches on a ruler. As tiny forces nudged the atom, the team could detect shifts in the pattern’s tilt and position. That gave them simultaneous data on momentum and position – without violating any laws. This technique isn’t just a quantum curiosity. It could sharpen ultra-precise sensors used for navigation, imaging, or even future spacecraft that explore where GPS can’t reach. As lead physicist Christophe Valahu put it, "We throw away the info we don’t need – so we can measure what we care about with greater precision." #RMScienceTechInvest #ScienceAdvances https://lnkd.in/d2hKZ_jx

Quantum state tomography, the process of reconstructing an unknown quantum state, traditionally suffers from computational demands that grow exponentially with system size, a significant barrier to progress in quantum technologies. S. M. Yousuf Iqbal Tomal and Abdullah Al Shafin, both from BRAC University, now present a new approach, geometric latent space tomography, which overcomes this limitation while crucially preserving the underlying geometric structure of quantum states. Their method combines classical neural networks with quantum circuit decoders, trained to ensure that distances within the network’s ‘latent space’ accurately reflect the true distances between quantum states, measured by the Bures distance. This innovative technique achieves high-fidelity reconstruction of quantum states and reveals an intrinsic, lower-dimensional structure within the complex space of quantum possibilities, offering substantial computational advantages and enabling direct state discrimination and improved error mitigation for quantum devices. https://lnkd.in/eSpH3YhD