---
title: "Physicists May Have Inadvertently Built a Qubit That Can Run Backward in Time"
url: "https://usubjects.com/article/physicists-may-have-inadvertently-built-a-qubit-that-can-run-backward-in-time-4391"
updated: "2026-10-26T16:05:56.519Z"
description: "Physicists reportedly created a qubit whose quantum state can be manipulated in a way that mathematically resembles running backward in time. The result concerns controlled quantum evolution, not sending people, information, or objects into the past, and no direct connection to UFO or paranormal phenomena has been established."
sources: ["https://www.sciencealert.com/physicists-may-have-inadvertently-built-a-qubit-that-can-run-backward-in-time"]
licence: "All rights reserved"
---

# Physicists May Have Inadvertently Built a Qubit That Can Run Backward in Time

Published: 2026-10-25  
Source: [r/abovethenormnews](https://www.sciencealert.com/physicists-may-have-inadvertently-built-a-qubit-that-can-run-backward-in-time)

### Overview

Physicists in South Korea have described a quantum system whose evolution can be controlled in two opposing temporal directions—a result that **mathematically resembles running a quantum process backward in time**. The work does not mean that a particle, object, or message was sent into the past. Instead, it concerns how a quantum state changes under carefully controlled conditions and how those changes can be represented in the equations of quantum mechanics.

The finding was reported by physicist Tai Hyun Yoon of Korea University in a new preprint published on October 24, 2026. Yoon argues that an experiment conducted by his team in 2018, originally designed for a different purpose, had already demonstrated the essential behavior of what he calls a **quantum vacuum-seeded single-photon time qubit**.

### What Is a “Time Qubit”?

The concept builds on a theoretical proposal introduced by Tel Aviv University physicist Yakov Bloch in a November 2025 preprint. A conventional qubit can exist in a superposition of two states, such as 0 and 1. A time qubit extends that idea to the direction of quantum evolution, allowing the system to occupy a superposition of processes that develop in opposite temporal directions.

The concept can be compared—cautiously—to a clock whose hands could move clockwise and counterclockwise at the same time. The analogy does not imply that time itself has been reversed. Rather, the relevant quantum interaction can be made to evolve according to equations associated with forward or reverse progression. Bloch proposed testing the idea by splitting a quantum particle along two paths, applying opposing magnetic fields, and then recombining the paths to study the resulting interference.

### How the Experiment Works

Yoon’s approach uses light rather than a spinning particle. The setup relies on two crystal sources that produce entangled photon pairs. One photon from each pair serves as the single-photon qubit, while the overall arrangement is described as **entangled nonlinear biphoton source, or ENBS, interferometry**.

In the experiment, researchers control the direction of a particular quantum interaction by adjusting the phase of the light used to generate the photons. Shifting that phase by half a cycle reverses the interaction’s mathematical direction. This does not cause time to flow backward; instead, it changes the sign of the interaction term that governs how the quantum state develops.

In quantum mechanics, that evolution is described by a Hamiltonian, the mathematical operator that determines how a system changes over time. Reversing the sign of a Hamiltonian can make the system evolve as though it were retracing its earlier behavior. Yoon’s method does not reverse the complete Hamiltonian of the universe—or even necessarily the entire photon system—but reverses the component associated with the controlled interaction.

### Implications and Limitations

The importance of the work lies in its potential relevance to **quantum information processing**. If researchers can place different directions of quantum evolution into a controlled superposition, such systems could offer new approaches to manipulating information, designing quantum simulations, or studying processes that are difficult to reproduce through ordinary forward-time evolution.

The result remains preliminary. Yoon’s analysis appears in a preprint, meaning it has not yet undergone the full peer-review process typically used to assess published research. Further experiments will be needed to confirm the interpretation and determine whether the system meets all the requirements of a time qubit rather than merely displaying reversible or phase-controlled quantum dynamics. **No evidence connects the work to time travel, paranormal claims, or unidentified aerial phenomena.**

## Provenance

This USUBJECTS page is a summary or digest of the linked original source. Any accompanying generated visual is an illustrative reconstruction, not evidence.