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When a chiral molecule absorbs light and releases an electron, the emitted electron can carry information about the molecule’s handedness through both its direction of motion and its spin. In this work, we show that these effects can be understood through a simple geometric picture: a small set of intrinsic molecular directions governs how the molecule’s handedness is transferred to the outgoing electron. This provides an intuitive way to understand the connection between molecular chirality and electron spin in photoionization.

When a chiral molecule absorbs light and releases an electron, the electron’s spin can become linked to the direction in which it moves. In this work, we study these spin–current correlations and show how they are shaped by the molecule’s handedness. The results reveal how chirality can connect electron motion and spin during photoionization, providing another route for understanding spin-dependent effects in chiral molecules.

When a chiral molecule absorbs light and releases an electron, the electron’s spin can become linked to the molecule’s orientation in a way that depends on its handedness. In this work, we identify an intrinsic molecular compass that governs this connection between molecular geometry and electron spin. The same underlying correlation explains both how molecular orientation can influence the emitted electron’s spin and, conversely, how selecting the electron spin can reveal information about the molecule’s orientation.

Quantum tunneling allows a particle to cross a barrier that it could not overcome according to classical physics, raising the question of how long the particle spends tunneling through it. In this work, we study this question using quantum time-of-arrival operators and show that the tunneling time is zero across a broad class of possible definitions of these operators. This demonstrates that the prediction of instantaneous tunneling is not simply an artifact of one particular mathematical construction.

Quantum tunneling allows a particle to pass through a barrier even when it does not have enough energy to cross it classically. A long-standing question is whether this process takes a finite amount of time or is effectively instantaneous, and the literature has not reached a clear consensus. In this work, we try to reconcile these different results by distinguishing between full tunneling from partial tunneling. We find that full tunneling is instantaneous within our framework, while partial tunneling takes a finite amount of time.

In quantum mechanics, even the question of when a particle arrives somewhere is surprisingly subtle, especially when relativity is involved. In this work, we construct a relativistic quantum description of arrival time for spin-0 particles and use it to study tunneling through an energy barrier. We find that, under the conditions considered, a relativistic particle can tunnel across the barrier with zero traversal time, suggesting that instantaneous tunneling can arise as a genuine quantum effect rather than from a particular approximation.

Earlier work using a nonrelativistic theory suggested that quantum tunneling can occur instantaneously, raising the question of whether this result survives once relativity is taken into account. In this work, we develop a relativistic description of quantum arrival time for spin-0 particles and use it to study tunneling through a barrier. We find that the components of the particle that truly tunnel through the barrier contribute zero traversal time, while only the components energetic enough to pass over the barrier take a finite time. This shows that instantaneous tunneling is not simply a consequence of using a nonrelativistic theory.

In quantum mechanics, predicting when a particle will arrive at a particular place is more subtle than it is in classical physics, especially when relativistic effects become important. In this work, we develop a relativistic quantum description of arrival time for massive spin-0 particles moving freely. We show how this framework can be used to construct arrival-time distributions and find that quantum particles may arrive earlier or later than classical physics would predict, while still remaining fully consistent with special relativity.

Galileo showed that a heavy object and a light one fall at the same rate, this is called the Weak Equivalence Principle. Here, we investigated whether this principle still holds for objects so small that quantum mechanics takes over. By working out when a quantum particle fired upward should arrive at a given point, we found that the arrival time has a small dependence on the particle's mass.

A quantum particle does not always arrive at a destination at exactly the time predicted by classical physics. In this work, we show that these quantum differences in arrival time can be reduced by carefully shaping the phase of the particle’s wave function. This makes it possible, in principle, to synchronize a quantum clock with a classical clock, showing how quantum effects in time measurements can be controlled rather than simply accepted as unavoidable.