Revenue from contracts with customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Total revenue	$ 2,562	$ 1,695	$ 5,852	$ 4,778
United States
Disaggregation of Revenue [Line Items]
Total revenue	1,083	951	1,814	2,461
Japan
Disaggregation of Revenue [Line Items]
Total revenue	299	293	920	1,008
Germany
Disaggregation of Revenue [Line Items]
Total revenue	287	237	865	757
Switzerland
Disaggregation of Revenue [Line Items]
Total revenue	311	0	686	0
Other
Disaggregation of Revenue [Line Items]
Total revenue	582	214	1,567	552
Revenue recognized over time
Disaggregation of Revenue [Line Items]
Total revenue	2,506	1,660	5,713	4,618
Revenue recognized at a point in time
Disaggregation of Revenue [Line Items]
Total revenue	56	35	139	160
QCaaS
Disaggregation of Revenue [Line Items]
Total revenue	1,132	1,346	3,333	3,905
Professional services
Disaggregation of Revenue [Line Items]
Total revenue	1,421	347	2,482	812
Other revenue
Disaggregation of Revenue [Line Items]
Total revenue	$ 9	$ 2	$ 37	$ 61