The fortunes of major quantum computing firms turned negative this week as share prices sank—in some cases by double digits.

The so-called Quantum Four publicly traded companies—Rigetti Computing, IonQ, Quantum Computing Inc, and D-Wave Quantum—saw their stock prices tumble on Thursday. And as of this writing, all four companies are down even lower in premarket trading on Friday.

Berkeley, California-based Rigetti (NASDAQ: RGTI) has seen the biggest drop, with its stock price falling almost 15% on Thursday, October 16. As of this writing, the stock was down another 7.65% during the premarket session.

Shares of IonQ (NYSE: IONQ) were down by a similar amount on Thursday, although their 2.23% drop on Friday has not been quite as steep.

Quantum Computing Inc (NASDAQ: QUBT) fell by 11.73%

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