The Quantum Eraser Does Not Always Erase (original) (raw)
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Control of quantum interference in the quantum eraser
We have implemented an optical quantum eraser with the aim of studying this phenomenon in the context of state discrimination. An interfering single photon is entangled with another one serving as a which-path marker. As a consequence, the visibility of the interference as well as the which-path information are constrained by the overlap (measured by the inner product) between the which-path marker states, which in a more general situation are non-orthogonal. In order to perform which-path or quantum eraser measurements while analyzing non-orthogonal states, we resort to a probabilistic method for the unambiguous modification of the inner product between the two states of the which-path marker in a discrimination-like process.
2021
C. Bracken,1, 2 J.R. Hance,3, ∗ and S. Hossenfelder4 Dept of Experimental Physics, Maynooth University, Maynooth, Co. Kildare, Ireland Astronomy & Astrophysics Section, School of Cosmic Physics, Dublin Institute for Advanced Studies, Fitzwilliam Place, Dublin 2, D02 XF86 Quantum Engineering Technology Laboratories, Department of Electrical and Electronic Engineering, University of Bristol, Woodland Road, Bristol, BS8 1US, UK Frankfurt Institute for Advanced Studies, Ruth-Moufang-Str. 1, D-60438 Frankfurt am Main, Germany (Dated: November 19, 2021)
Quantum Interference, State Engineering, and Quantum Eraser
Annals of the New York Academy of Sciences, 1995
To summarize in one pregnant sentence the most recent result has always been and still is the requirement every scientist has to fulfill when he or she wants to explain his or her research to John A. Wheeler, the great scientist, deep philosopher, and extraordinary human being we honor at this conference. The central lesson of quantum mechanics, that is, interfering transition probability amplitudes rather than probabilities, stands out nowhere clearer than in the double-slit experiment, the center of the long-standing debate between Bohr and Einstein.I Nobody has identified this simple, but far-reaching difference between classical and quantum physics as the origin of so many different physical phenomena ranging from nuclear physics2 via rainbow scattering3s4 to squeezed state physics5 as John A. Wheeler. Nothing is more appropriate at a conference celebrating this great man than to present yet another illustration of this one-sentence summary-path information implies probabilities, whereas no path information implies interfering probability amplitudes.
The ‘Delayed Choice Quantum Eraser’ Neither Erases Nor Delays
Foundations of Physics
It is demonstrated that 'quantum eraser' (QE) experiments do not erase any information. Nor do they demonstrate 'temporal nonlocality' in their 'delayed choice' form, beyond standard EPR correlations. It is shown that the erroneous erasure claims arise from assuming that the improper mixed state of the signal photon physically prefers either the 'which way' or 'both ways' basis, when no such preference is warranted. The latter point is illustrated through comparison of the QE spatial state space with the spin-1/2 space of particles in the EPR-spin experiment. I. THE 'QUANTUM ERASER' EXPERIMENT: INTRODUCTION The so-called 'quantum eraser' experiment ('QE'), first introduced in Kim et al (2000), involves a pair of entangled quanta (usually photons). One of these, called the signal (or 'system') photon s, is directed to a two-slit or two-arm apparatus and the other, the idler (or 'environment') photon p, is directed to a set of detectors equipped for various measurement options (or is subjected to polarization manipulations before detection). The 'delayed' version of the experiment consists of detecting s prior to p.
What is Erased in the Quantum Erasure?
Foundations of Physics, 2006
In this paper we re-examine a series of gedanken welcher Weg (WW) experiments introduced by Scully, Englert and Walther that contain the essential ideas underlying the quantum eraser. For this purpose we use the Bohm model which gives a sharp picture of the behaviour of the atoms involved in these experiments. This model supports the thesis that interference disappears in such WW experiments, even though the centre of mass wave function remains coherent throughout the experiment. It also shows exactly what it means to say "that the interference can be restored by manipulating the WW detectors long after the atoms have passed." It does not support Wheeler's notion that "the past is undefined and undefinable without the observation [in the present]"
A delayed choice quantum eraser explained by the transactional interpretation of quantum mechanics
This paper explains the delayed choice quantum eraser of Kim et al. [1] in terms of the transactional interpretation of quantum mechanics by John Cramer [2, 3]. It is kept deliberately mathematically simple to help explain the transactional technique. The emphasis is on a clear understanding of how the instantaneous "collapse" of the wave function due to a measurement at a specific time and place may be reinterpreted as a relativistically well-defined collapse over the entire path of the photon and over the entire transit time from slit to detector. This is made possible by the use of a retarded offer wave, which is thought to travel from the slits (or rather the small region within the parametric crystal where down-conversion takes place) to the detector and an advanced counter wave traveling backward in time from the detector to the slits. The point here is to make clear how simple the transactional picture is and how much more intuitive the collapse of the wave function becomes if viewed in this way. Also, any confusion about possible retro-causal signaling is put to rest. A delayed choice quantum eraser does not require any sort of backward in time communication. This paper makes the point that it is preferable to use the Transactional Interpretation (TI) over the usual Copenhagen Interpretation (CI) for a more intuitive understanding of the quantum eraser delayed choice experiment. Both methods give exactly the same end results and can be used interchangeably.
arXiv (Cornell University), 2022
We utilize IBM's quantum computers to perform a full quantum simulation of the optical quantum eraser (QE) utilizing a Mach-Zehnder interferometer with a variable partially-polarizing beam splitter (VPPBS) at the input. The use of the VPPBS motivates us to introduce the entangled quantum eraser, for which the path information is erased using a Bell-basis measurement. We also investigate the behavior of the wave aspect, i.e., the quantum coherence, as well as the particle character, represented by the predictability and entanglement, as delineated in complete complementarity relations (CCRs). As we show in this article, the utilization of the VPPBS uncover interesting aspects of the QE and CCRs. For instance, we can recover the full wave-behavior by the erasure procedure even when we have only partial knowledge about the path through entanglement.
Comprehensive experimental test of quantum erasure
The European Physical Journal D - Atomic, Molecular and Optical Physics, 2002
In an interferometer, path information and interference visibility are incompatible quantities. Complete determination of the path will exclude any possibility of interference, rendering the visibility zero. However, if the composite object and probe state is pure, it is, under certain conditions, possible to trade the path information for improved (conditioned) visibility. Such a procedure is called quantum erasure. We have performed such experiments with polarization entangled photon pairs. Using a partial polarizer we could vary the degree of entanglement between object and probe. We could also vary the interferometer splitting ratio and thereby vary the a priori path predictability. We have tested quantum erasure under a number of different experimental conditions and found good agreement between experiments and theory.
Observations of the Delayed-Choice Quantum Eraser in a Macroscopic System
SSRN Electronic Journal
The heart of quantum mechanics is quantum superposition, satisfying the complementarity theory between the particle and wave natures of a physical entity. Delayed choice experiments result in the violation of the cause-effect relation between which-path information (particle nature) and fringe visibility (wave nature). Quantum eraser is for the reversal of predetermined photon characteristics via post-measurements. Here, a macroscopic delayed-choice quantum eraser is conducted using a continuous wave laser to challenge the quantum mystery. Unlike most delayed-choice experiments, the present observations are for the output photon's polarization control. As a result, the physics of the quantum eraser is found in selective measurements. To support this understanding, analytical solutions for the macroscopic quantum eraser are sought. Thus, the delayed-choice quantum eraser becomes deterministic and macroscopic in a limited interferometer such as a Mach-Zehnder interferometer, where the violation of the cause-effect relation is just a measurement illusion.