Can Markets Price Quantum Risk? Equity Valuation and Stock Reactions to Quantum Breakthrough Announcements

This paper examines how equity markets react when quantum technology breakthroughs are publicly announced and whether these reactions represent a distinct and priced source of financial risk. Unlike mature technologies that progress through steady incremental improvements, quantum computing advances through rare but highly consequential scientific milestones such as changes in qubit architectures, improvements in error correction performance and progress in system scalability. Each announcement condenses substantial technical uncertainty into a single moment, often triggering rapid investor reassessments about future feasibility and commercial timelines. To study these dynamics, we construct a hand collected dataset of verified quantum chip announcements made by nine publicly listed firms between 2019 and 2024 and analyze market responses using an event study framework. Firm level abnormal returns are estimated through rolling market model regressions with robust statistical inference, allowing market reactions to be isolated from broader market movements. Announcement period abnormal returns are aggregated into a daily quantum factor $Q_t$ designed to capture the immediate market impact of quantum technology news while avoiding artificial persistence. The analysis evaluates how firm level exposure to this factor varies across companies and tests whether such exposure carries pricing relevance using cross sectional regressions with bootstrap validation suited to the small specialized sample. The empirical results show that quantum technology announcements generate sharp and statistically significant price reactions that dissipate quickly after disclosure, consistent with rapid belief updating rather than long term repricing. The constructed quantum factor exhibits low persistence, elevated volatility and pronounced tail behavior, indicating that quantum breakthroughs arrive as episodic information shocks rather than persistent economic states. Firms more directly involved in quantum hardware development display stronger announcement period sensitivity.