| In millions, except per share items | Jun-30-23 | Dec-31-22 | Sep-30-22 | Jun-30-22 | Mar-31-22 | Dec-31-21 | Sep-30-21 | Jun-30-21 |
| | 10-Q/A | 8-K | 10-Q | 10-Q/A | 10-Q | 10-K | 10-Q | 10-Q |
| Revenue from contract with customer, product and service, extensible enumeration | | | | | | | | |
| Service revenue | 1.7 | 0.1 | 0.1 | 0.1 | | | 0.2 | |
| Service revenue growth | 3310.0% | | -35.5% | | -100.0% | -100.0% | | |
| Cost of revenue | 0.4 | | 0.0 | 0.0 | | -0.1 | -0.2 | |
| Gross profit | 1.3 | 0.1 | 0.1 | 0.0 | | | 0.4 | |
| Gross margin | 77.2% | 100.0% | 89.1% | 76.0% | | | 192.0% | |
| |
| Operating expenses: | | | | | | | | |
| Research and development expenses | 10.2 | 10.3 | 10.6 | 10.9 | 10.0 | 11.6 | 9.0 | 20.8 |
| Selling, general and administrative expenses | 10.0 | 10.9 | 11.2 | 12.9 | 14.9 | 13.1 | 12.1 | 9.7 |
| Total operating expenses | 20.2 | 21.2 | 43.8 | 23.8 | 50.4 | 133.6 | 44.4 | 64.6 |
| Loss from operations | -18.9 | -21.1 | -21.6 | -23.7 | -24.8 | -24.7 | -20.7 | -30.5 |
| Operating margin | -1108.2% | -17576.7% | -16775.2% | -47438.0% | | | -10360.5% | |
| |
| Other income (expense): | | | | | | | | |
| Change in fair value of warrant liability | 0.5 | | 1.6 | 2.3 | -0.5 | | -2.7 | 4.5 |
| Realized (loss) gain on disposal of asset | 0.0 | | 0.0 | 0.0 | -0.1 | 0.0 | | |
| Interest income | 0.4 | 0.5 | 0.0 | 0.0 | | | | 0.0 |
| Interest expense | -0.7 | | -1.3 | -1.4 | -1.5 | | -4.3 | -3.4 |
| Litigation settlement, net | | | | | | -7.0 | | -7.0 |
| Other income | | 0.0 | 0.0 | | 0.0 | -5.0 | -4.8 | 0.0 |
| Total other income (expense) | 0.1 | 0.0 | 0.3 | 0.8 | -2.0 | | 15.1 | 94.9 |
| Net loss | -18.8 | -24.4 | -21.3 | -22.9 | -26.8 | | -5.6 | 64.3 |
| |
| Net loss per share, basic (in dollars per share) | ($0.20) | ($0.30) | ($0.26) | ($0.28) | ($0.34) | | ($0.09) | $1.25 |
| Net loss per share, fully diluted (in dollars per share) | ($0.20) | ($0.30) | ($0.26) | ($0.28) | ($0.34) | | ($0.09) | ($0.59) |
| |
| Weighted average shares outstanding, basic (in shares) | 96.0 | 82.8 | 82.1 | 81.3 | 80.0 | 65.2 | 60.6 | 51.5 |
| Weighted average shares outstanding, fully diluted (in shares) | 96.0 | 82.8 | 82.1 | 81.3 | 80.0 | 70.9 | 60.6 | 69.7 |