According to our current understanding of quantum mechanics, there is a non-zero probability that a tennis ball, or any macroscopic object, could quantum tunnel through a wall. However, the probability of such an event occurring for macroscopic objects like tennis balls is extraordinarily small, practically negligible in most cases.
Quantum tunneling is a phenomenon where a particle can pass through a potential barrier, such as a wall, even though it does not possess enough energy to surmount the barrier based on classical physics. In quantum mechanics, particles are described by wave functions that extend through space, and there is always a small probability that the particle can be found on the other side of the barrier due to the wave-like nature of matter.
However, for macroscopic objects like tennis balls, the wave function is highly localized and rapidly decoheres due to interactions with the environment. This decoherence leads to the suppression of quantum effects at the macroscopic scale, and the probability of observing macroscopic objects quantum tunneling through barriers becomes vanishingly small.
While quantum tunneling has been observed and well-documented for microscopic particles, such as electrons or photons, its effects are negligible for everyday objects governed by classical mechanics. The energy required for a macroscopic object like a tennis ball to tunnel through a wall is astronomically large, making it effectively impossible in practice.
It's worth noting that the behavior of quantum systems is inherently probabilistic, and given an infinite number of trials, there is a non-zero probability for any event to occur, including extremely unlikely events. However, in the case of a macroscopic object like a tennis ball tunneling through a wall, the probability is so close to zero that it is essentially negligible within the confines of our current understanding and the scale of our observable universe.